I have mixed colors from the basic set to make the color I wanted and found that to be pretty easy. Additionally, I find that the transparent or semi-transparent paints let me build up layers of color for a more organic look.
I don't air brush, or spray paint. I do use latex paint tho, brushed on, and often mix 'custom' colors. Like Oliver said, it's easy. However, if you want to duplicate a 'custom' color later, you had better write down all your quantities of each color, or you could be days coming up with the desired color. Either that, or mix up a whole lot at once. when I paint my figures, not real large, I don't use a lot of paint, so anything mixed could be just drops of each color, or possibly plastic spoonfuls, a little goes a long way for me.
And for colors I only use the three basic colors, red, yellow, and blue. And dark green, white, and black. Hehehe I get the darkest blue and green I can get, you can always lighten them up with white, but I have found it is impossible to mix a decent green or blue. Same with black, you cannot mix a suitable black. With those six colors I can come up with about any color you can think of. Except orange, for some strange reason when I tried mixing orange, I could only come up with various shades of pink. Hell, I was even using color wheels, and could still only get pink. So, wound up buying a can of orange. xz
"It ain't what you're told, it's what you know." - Granny Weatherwax
Fawkahwe tribal police SWAT Team
Some days, the supply of available curse words is insufficient to meet my demands.
.....Call me a craftsman, artisan, or artistic, and I will accept that. Call me an artist and you will likely get a quite rude comment in return. I am not a @#$%ing artist.