If you really want to see colour in action, I think Wasily Kandinsky is the painter to study.
Here's one of his abstracts. It's 127x200cm and was painted in 1925.
|dare 39, light grey shading|
|dare 39 +yellow added digitally|
|dare 39 (printed, some red added with pen, then rescanned)|
|red-yellow-blue (blue added digitally)|
|my monochrome version with orange (colour enhanced)|
|my full colour version|