There are no strict rules for pouring. If you want a full range of colours, you will have to chose a colour from each of the three main categories; red, blue, yellow, and I personally go for SINGLE PIGMENTS because if they are already blends of pigments I am not using basic colours. This doesn't mean I shouldn't, but I need to realize that mixed pigment paints go different ways from single pigments! A good example of this is Indigo, which is not a single pigment! Paynes Grey and Neutral Tint are two other much used paints which actually contain black, as does Indigo. I would not want to pour with those colours unless I am looking for effects that can only be attained with a black component.
The rule that watercolour paintings may not contain black is fortunately antiquated. The rule that white in watercolours is always the colour of the paper is also out of date.This is especially good because watercolour paper is often ivory coloured. so if you are painting a snow scene without using white - perfectly possible - choose white paper! Many accomplished watercolourists use white gouache (or Chinese white) to enhance or reinstate highlights. It is not normally used for pouring though it's usful if things get really out of hand! But once you involve white in pouring you are using pastel colours.
Of course, you don't have to choose three basic colours to pour with, though I tend to avoid green and orange. Green is a problem in all mediums. Green out of the tube is disliked by many artists. To make a really good olive green you could use a clear yellow and black; for a bright green just do some experimenting. Remember that some yellows are a bit reddish, so it's harder to mix green with them. Depending on the make, ultramarine is not usually ideal for mixing green due to its red/purple tinge. Black pourings are actually sensational, but that is not really what watercolour is all about and you would probably end up with a shade of grey depending on how much pigment you pour! If you are looking for translucency in your pourings DO NOT use thick paint. It is better to make layers than try to achieve all possible effects in one go.
Incidentally, almost any three colours will eventually produce black (if intensive enough) or grey as a tertiary - or mud if you really got it wrong i.e. if you don't want a muddy painting! Secondary colours include green, orange and purple. Consult a colour chart for exact information. There are plenty of them around. Almost every book on painting includes one.
I will not start talking about warm and cool colours. That choice is a matter of trial and error till you get what you want. For this a colour chart is useful, but should show how the colours work when layered.
|This shows a little editing to emphasize certain areas. The details below are taken from this image.|
Isopropyl disoved pigment while it is creeping through the wet paint. It's fascinating to watch, but if the paint is too wet you will find it closing in on the isopropyl effects and often destroying them. It's really a matter of trial and error.
You don't have to use isopropyl. It isn't always a good idea!
|little dragon, oils, started with several colours.|
When the pouring sequence is over, you will have to decide what to do next. Is it going to be an abstract? If it's figurative, do the colours make sense? Have you got the colour balance you want? Would adding another colour improve the result? Or would you prefer to take it to the bathroom and run it under cold water, using a nail brush to remove the paint? Depending on whether you have used staining paints, you will be left with a little or nothing of that pouring. but sometimes it's the road you have to go down.