The subject of colour mixing, especially with watercolour, is a great passion of mine and there are many excellent sites which explain it well. I didn't really understand colour until I read "Blue and Yellow Don't Make Green" which is a kind of industry standard. I thought that colour mixing was rather like the additive colours of Red, Blue and Green on a TV screen but in reverse, on paper. Then I realised that the only reason one gets Green by mixing Blue and Yellow is because of the "impurities" (ie Green) in the Blue and Yellow paints. Similarly with the other primaries. I really like the idea of a 6-colour palette because it reinforces this theory really well. One only gets a decent Green by mixing a Blue which "leans" towards Green and a Yellow which does the same.
A cook would tend to use pure materials for preparing dishes rather than ready-made meals (such as I would use!) The same goes for colour. If I were an art teacher, (I think I would be something of a tyrant!) I would tell my students to get to know and love the names of original pigments and use them as a kind of colour toolbox. I would tell them to avoid ready-mixed paints, Sap Green is often used as an example; each manufacturer has its own version. Most of my greens (we're not talking about food now) originate from a powerful green such as Viridian or Winsor Green which is rather too strong and "acid" to be used on its own. But, mixed with various yellows and browns, it produces a marvellous range of greens. Add a little red (the complement of green) to darken the colour. Winsor & Newton Winsor Blue (Green Shade) is another pure pigment to mix with yellows to produce greens.
Also, as my imaginary art teacher, I would tell my students that, since they have saved lots of money by buying only six or so colours, then they can afford to buy Artists' Quality paints. Even if you are starting out, if you can afford it, treat yourself to decent materials and it will inspire you.
I really don't like Cadmium Yellow, it is opaque and produces a chalky finish. So I went on the search for a transparent yellow and came across Azo Yellow Medium from Rembrandt which is superb. I feel the same about Cadmium Red and Cadmium Orange which are also rather opaque. Rembrandt paints are available in the art shops here in Girona but I'm not sure where to buy them in other parts of the world. Rembrandt is the Royal Talens artists' grade, Van Gough is the students' grade.
So, my suggested 6-colour palette would be the following:
Red: (Rembrandt) Permanent Red Light and Quinacridrone Rose or (W&N) Cadmium Red and Magenta. (But I find Cadmium Red tends to be opaque so it's worth looking for a more transparent red).
Yellow: Azo Yellow Medium and Lemon Yellow.
Blue: Cobalt Blue and Cerulean Blue.
But I would cheat and add a green, but only one. I would include Viridian or Winsor Green which I mentioned above.
But I write this in all humility; this is only what I've found and there are many suggestions by artists and teachers on the internet or in books. In any case, what you find best for you is the most important thing! Anyway, I must own up and say that I have far more than 7 colours in my box (we're talking about watercolours here).
So, my suggested 6-colour palette would be the following:
Red: (Rembrandt) Permanent Red Light and Quinacridrone Rose or (W&N) Cadmium Red and Magenta. (But I find Cadmium Red tends to be opaque so it's worth looking for a more transparent red).
Yellow: Azo Yellow Medium and Lemon Yellow.
Blue: Cobalt Blue and Cerulean Blue.
But I would cheat and add a green, but only one. I would include Viridian or Winsor Green which I mentioned above.
But I write this in all humility; this is only what I've found and there are many suggestions by artists and teachers on the internet or in books. In any case, what you find best for you is the most important thing! Anyway, I must own up and say that I have far more than 7 colours in my box (we're talking about watercolours here).
Another favourite book of mine is "Making Color Sing". I usually have blobs of the three primaries of Red, Blue and Yellow arranged in a circle in my paint box tray and use them to create an array of greys by "dragging" bits of each colour into the centre of the circle.
For blacks, I don't use black. I've used Paynes Grey from time to time but it produces images which are just too strong. Instead I start with an empty whole pan and squirt two complementary colours into each end of the plastic pan and mix them in the middle. Blue and Brown aren't exactly complements but they make a nice range of darkness which is similar to Paynes Grey. Quinacridone Red and Viridian make a marvellous deep nothingness! When mixing colours, don't mix them too thoroughly, let a bit of the original colours remain. This makes a much more interesting result.
Paper
One problem that I have hit regarding paper is that, sometimes, a paper will become absorbent (or else it was always that way). This is a disaster for watercolours as the paint rapidly gets sucked into the paper as if it were a sponge rather than remaining on the surface for a while (to enable it to be mixed with other colours, for example). The result is a very dull colour. I found some of my expensive papers have done this, whether it's because of a damp environment or for other reasons I don't know. But I always test my paper in all four corners with a blob of dilute paint before starting. I used a paper recently which was ok on the left hand side but it was was absorbent on the right! I reckon my test blobs should remain on the surface for at least a minute. I just tested one of my favourite papers and, after two minutes, the paint is still wet on the surface.
I haven't put any links on this posting as I'm sure you can search for all these things yourself. Good luck!
One problem that I have hit regarding paper is that, sometimes, a paper will become absorbent (or else it was always that way). This is a disaster for watercolours as the paint rapidly gets sucked into the paper as if it were a sponge rather than remaining on the surface for a while (to enable it to be mixed with other colours, for example). The result is a very dull colour. I found some of my expensive papers have done this, whether it's because of a damp environment or for other reasons I don't know. But I always test my paper in all four corners with a blob of dilute paint before starting. I used a paper recently which was ok on the left hand side but it was was absorbent on the right! I reckon my test blobs should remain on the surface for at least a minute. I just tested one of my favourite papers and, after two minutes, the paint is still wet on the surface.
I haven't put any links on this posting as I'm sure you can search for all these things yourself. Good luck!