COLOUR: MUD
One of the things painters often worry about  is getting muddy colours, dirty colours.
You will read about this danger in books and magazines: DANGER!! MUDDY COLOURS!!
The first thing to say is that this is partly a matter of opinion and taste;
Some artists like clean, fresh, vibrant colours, others like more earthy characterful colours.
                                                                                       Aubrey Philips top Hazel Soan lower.

So be careful not to be unduly influenced by what others say, look at different artists and get a sense of what you like.
NEVERTHELESS; there is truth in the warning, it is possibly to arrive at a stage when your painting has lost its sparkle, its liveliness. it is overworked and the colours look dull. This is more a problem in watercolour than other mediums for a number of reasons and it is easier to fix in opaque mEdiums like acrylic or oil paint. But you can still get dirty looking colours in any medium.
there are three main issues:
1. the colours you use, and especially the colours you mix.
2. the way you apply the paint
3. the number of colours you layer.

1. COLOUR
Some colours are prone to muddiness, the more dense colours, some browns all the cadmiums, yellow ochre in particular, ultramarine blue, sap green, and of course black. Light red is a very dense colour.These are not 'wrong' or 'bad'  colours, there are no colours you can't successfully use,  but there are  colours you need to be careful with

Some artists choose colours which are particularly transparent; permanent rose, lemon yellow, phthalo blue, viridian.   For some this is way too bright, (but they can of course  be subdued by careful mixing)
I usually say: learn to use whatever colours you have, but be aware of the colours which cause you problems. There is no bad colour, but if you identify the colours and especially their mixtures which cause you problems you can work on improving either by substituting other colours or using those problem colours in a better way.

MIXING

Some colours are fine on their own but when mixed cause problems, ultramarine is a good blue but it can react with other colours to make effects which you may like or not like, with brown in particular it can go grainy,  (granulate to use the term people seem to like), this can be a good effect for a moody sky, or it can lead to a dirty looking colour. Sap green is to me a nice green but mixed with too many other colours it can go dull. There is a point mixing two or three transparent colours is usually no problem mixing together two or three of the more opaque colours can be a problem, ( but not necessarily, try it and see for yourself)

Some colours are simple and some are more complex, so lemon yellow is a simple colour, it is really one colour, yellow ochre is a complex colour, it is yellow but it brownish yellow, so it has bit of red and blue in as well. kind of hidden colours, so when you mix a complex colour with other colours you are mixing more colours than you may think.  Mix two complex colours and you have more likelihood of getting a dirty looking mix. 

 SOME ARTISTS WILL SUBSTITUTE A CLEANER BUT SIMILAR COLOUR, SO RAW SIENNA IS SIMILAR TO YELLOW OCHRE BUT IT IS MORE TRANSPARENT, lemon yellow with a touch if permanent rose may give a more transparent substitute for cadmium yellow. If you have trouble with brown, I find Burnt Sienna to be a cleaner mixing brown than Burnt Umber, but some artists would avoid brown altogether and mix it from transparent colours. (But as ever, you will find good painters using browns very successfully).

YELLOW: this may seem surprising but , especially in watercolour, yellow on top of other colours can produce a dull effect. It  best not used as a glaze over other colours to try and brighten,  put yellow on first, then other colours . Of course this isn't a law, try it and see. 

2. The way you apply the paint, if you watch a video of an artist,especially a watercolourist, you may note that they often have a light touch, their brush sort of dances across the paper, they don't scrub in the paint, they don't keep dabbing it and messing with it, they put it on fluidly and leave it to dry before applying the next layer. Colours are not in themselves muddy it is how we mess them around keeping touching them, especially when they are beginning to dry. Try and paint fluidly and don't keep dabbing and prodding the paint.

3. LAYERS,this is particularly important for watercolour, in fact muddy colours in other mediums can readily be fixed by a cleaner layer of paint being added once the dull layer is dry (some artists even paint a dull underpainting so their brighter colours can sit on top, giving the painting more depth). Watercolour being essentially a transparent medium this is not so easy.

I think in a successful watercolour some areas may have only one layer (some artists always leave at least a little white paper untouched), some areas with two layers; fewer areas with 3 layers, and only a small amount 4 or more. The more layers the more likely you get a dull clogged up. 

NOW THIS IS IMPORTANT: A VERY EXPERIENCED WATERCOLOURIST WILL FIND WAYS OF CONTROLLING THIS AND BE ABLE TO BUILD UP MANY LAYERS WITHOUT TROUBLE, SO THIS ISN'T AN ABSOLUTE RULE. The great thing about art is you can't do much harm whatever you do, so feel free to experiment with how many layers you can build up, the best way to learn is to do it, and reflect on the results.

Try a few versions of a picture. 

1. using colours which may produce muddy effect: ultramarine burnt umber yellow ochre, cadmium yellow.

2. Now try it with phthalo blue or cobalt blue if you haven't got phthalo (remember this blue has at least 3 names: Intense Blue, Winsor Blue, all the same colour), burnt sienna and raw sienna, and lemon yellow.

3 Build up a dark painting using  earthly colour such as burnt umber plus a little ultramarine in one strong wash

Now try to get that dark in 3 or 4 layers to  contrast the effects. You may like the more layered one, there isn't really a right or wrong but learn to recognise the kind of colour effects which you like, identify what you want to improve.  

I PAINTED A MUDDY PAINTING, WHAT CAN I DO?

1. You can wash off some of the paint, best be bold really and run the whole painting under a tap, but if there is only one area of an otherwise nice painting you may want to just carefully wet that area with clean water, and dab, don't scrub, the area with kitchen roll. The surface colour will come off leaving a softer stain. let it dry and re paint.

2. Some artists reckon if an area has gone dull you can glaze it with a clean bright transparent colour. I am not sure about  this but give it a try. 

APPENDIX 1. MY EFFORT AT CREATING MUDDINESS.

Here are a pair of pairs! something I have always found difficult is painting 'wrong' on purpose, (I get it wrong readily when I am trying to paint right)  here I have tried to do the scenes on the left with fewer layers and lighter brushwork, the ones on the right I have tried to overwork. As I said at the beginning it is at least partly a matter of personal taste and opinion whether one pair is better.

COLOUR TRIADS
TRIADS, not the far eastern mafia but three colours.
When you have lots of colours it can get confusing , some artists like to see what they can do with three colours (plus black and white if needed, (not always needed, you can usually mix a black wiht your triad choices, and  white is not needed  in watercolour)
a basic triad would be Ultramarine, lemon yellow and alizarin crimson .
Try it on a simple picture this, or one of your own.

You could change it by just changing one colour, replace ultramarine with prussian blue or Phthalo blue, replace the red or the yellow.

Other triads
a very bright one: phthalo blue, lemon yellow, permanent rose
a deep earthy one: Prussian blue, crimson and yellow ochre.
A dark one:  Paynes grey, crimson, burnt sienna.
You can combine any 3,
An unusual one: Black, cadmium red, cadmium yellow

Experiment and enjoy your colours, if you get a result you especially like repeat! or you will not learn. Repeat repeat!

DRAW A TREE

A single tree will have many hundreds of leaves, in a glance you see them all, well all that are facing you. It can be confusing: how do I draw that thing which is one and many at the same time?

As well as looking, you need some kind of pattern to help you. I often think to draw you need to organise what you see in your head, sort of take it apart and re-assemble it.

You see detail, it is what our eyes are good at, but to draw something complex or manifold, if that's the word, you need to simplify it into stages.

1. Start with the idea of a tree, a bit like a lollipop. The direction of the light usually coming from above, will determine the shadow/shading.

2. A real tree will of course have more shape, a leafy shape.

It is worth getting familiar with a sort of made up template for a tree. then applying what you understand to a real tree.

3. When looking at a real tree it may be helpful to imagine it wrapped in cellophane see the simplified overall shape.

4. Then note that it is divided into a number of smaller shapes, a bit like a man carrying lots of  cloud shaped balloons. Each shape is a bunch of leaves on the network of twigs on a single branch, but these smaller shapes add up to a single tree shape. 

5. These shapes have a light side, usually the top and a shady underside, and they will often overlap, the light top of one bit meeting the shade of the bit behind and above. 

6. You may want to add a suggestion of leafy-ness to your marks.

 Now some artists like leafy looking trees,others like to simplify  into blocks of light and shade, do look at different artists, this helps you see that there is a style for you, remember you don't have to draw every leaf- you are not a human photocopier or camera; we have machines for that, you can work in a way that suits your skill level and artistic preferences.  Or if you are like me, sometimes you are a bit lazy and want to do things simply other times you want the challenge of looking harder and focusing with all your powers.

 Here are two  efforts of mine the first is more textured with a suggestion of leaves, but not losing the structure, the second I have  focused on the structure described in shape, light and shade.

we have used this photo for years as a drawing exercise , yes it is meant to be upside down if you do print it off keep it upside down, the point is to hinder you thinking about what it is and focusing on what the shapes and proportions are. The theory being that when you think, it is several ladies you stop looking at the shapes lines proportions and think of the subject. Do it same size start at one corner one shape at a time assessing the line and shape, its size angle etc. then the next shape then the next. It can be done with varying degrees of accuracy and concentration so if you want to be very strict, then go for it concentrate as fully as you can, but you will find you can be a little less rigid and still get good results, enjoy each shape see it as a full and goodly shape and give each shape it's due. You can turn it round at the end. And as with all exercise repetition is good, you can use a different picture of course one with good strong shapes

Gave it a go, Using acrylics means blending has to be done fairly quickly. I did find the video helpful starting with the highlight and blending around with darker colour.

Still thinking about colour, I did think for those who have done a lot of colour mixing and who may want more of a challenge looking at how to paint metallic objects may be interesting, I gave it a go this morning, trying to paint a gold ring and it was a disaster! so back to the drawing (painting ) board for me! meanwhile found this, there are lots of very generous people online sharing how to draw and paint do use them for when your teacher fails. This is oil paint which gives us a lot of time to blend whereas if you use acrylic of course it dries quickly so the same blending isn't possible unless you work quickly, it would work well I think in pastel.

Two things to note:1. you don't need metallic paint! it is just colours and tones. 2. note how much darkness there is, when he first puts the dark colour I thought that doesn't look like gold/brass, but be patient, in fact in shiny metal only a small area is light and your brain think s it is seeing lots of light shiny stuff.
of course this bloke is good, and makes it look easy, don't be hard on yourself if it doesn't look brilliant first time. but give it a go.

https://www.google.com/search?q=how+to+paint+gold&rlz=1C1RFPM_en-gbGB848GB849&oq=how+to+paint+gold&aqs=chrome..69i57j0l7.6079j0j7&sourceid=chrome&ie=UTF-8&fbclid=IwAR3pGvMQDUNihfYlH1CizvJ7tRGPXb-kTZX3WPoXRX9DFim44MWa1__rnCs#kpvalbx=_UEGUXpjJJ42_gQbb8qrAAw69

Gable ends can be a challenge, there are angles the eye doesn't pick up, you have to know they are there. If this isn't clear do let me know, there will be more!

DRAW ANYTHING JUST DRAW. 

One of 

the 

best 

ways to improve is repetition, you don't get fit by doing an exercise once. But thoughtful repetition i.e. can I improve, so here is version one and version two, I think version two is a slight improvement. 

A few more green photo's  Remember it is not necessary to match exactly but to try and get a range of greens which work in a painting, and which you personally like. Also a painting by Adrian Berg, I like his style, playful, recognisable but not photographic, kind of jolly.

COLOUR: MIXING AND MODIFYING GREEN

Green seems to be a challenge to many, me inlcuded, maybe because it is such a natural colour and paint is by definition artificial, so it is easy to try and paint a landscape and get an artificial looking result.

Of course there is no such thing as a wrong colour but for the kind of painting you are trying to achieve you need to get the colour to fit. Like in music there are no wrong notes on an instrument but you proabably want to play in key and in tune.
Some artists like very bright vivid colours, David Hockney some of Van Gogh, and many others.

If you compare these with older art you can see a big  difference, in the older art the grees is much less green, more subdued.
 Willelm Roleof
Even the Impressionists were fairly gentle in their use of green, here's Monet's famous poppy field. 

You will find a lot of contemporary artists like to keep their greens under control but it is ok to go a bit wild and think 'I want my greens to be vibrant'. It is good to get to know the kind of colours you like, you don't have to paint like everyone else.

Anyway it is good to know what greens you have, what they look like and what range of greens they mix.
While I like to think we can use all our colours it is ok to  find what you like and stick to it, there are lots of artists who never touch viridian or emerald finding them far too vivid. And for some artsits a noaaow range of light dark and middle green is sufficient.
Some never use ready made greens at all prefering to mix them from blues and yellows.

Essentially you need a starting green, a light and pale green,then a light and bright, deeper greens, warm green, autumnal greens, cool green, dark greens, and grey-greens.
I've started with Sap green and put out what I want to modify it with: lighter side: Lemon yellow, Cadmium Yellow, Raw Sienna (yellow ochre will do a similar job) Cadmium Orange, Alizarin Crimson, on the other side, Ultramarine, Burnt Umber, Black (Payne's grey will give an even stronger dark green)

DO MAKE NOTES AS YOU MIX, I HAVE ALSO PUT THE COLOURS on neat WHICH  I AM MIXING WITH

You will see I haven't attempted to match the colours but to get the kind of colours I see, lighter and paler in the background, lighter and brighter in the foreground, pale blue-greens for horizon trees. Very dark greens for big trees, browner greens for row of trees and shrubs.

Don't worry about matching my colours (I think I could do better!) but try and see from what you can mix, what suits the different areas.

more colour

A few small studies in colour first making a range of yellows mixing lemon yellow with very small amounts of crimson and blue and white, (this is acrylic), but trying to keep it within the range of recognisable yellow. then the same with red, modifying but trying to keep it looking red. Yellow has a narrow range add just a tiny bit much blue and it no longer looks yellow, same with adding too much red so it is an exercise in subtle thoughtful mixing. 

colour modifying.

This post is about modifying colour, it is colour mixing, but carefully, so that you keep the colour still looking blue, using blue, I was using acrylic, and used cyan crimson and lemon yellow, and white. The idea is to modify the blue with small amounts of the other colours but keeping within the range of blue. so a little bit of red, , then same with some white, then a little bit of lemon, then same with white, then a little bit of red and lemon, and again same with a white. 

Finally I tried to mix as dark as I could, obviously no white this time mostly blue and red with a little lemon, too much of the latter would lighten it, you ought to be able to get something quite dark. Then add white to see if you have got a grey.

The point of this is to mix colours in a controlled manner making small but visible modifications. Colour mixing step by step.