Color theory is a good foundation for painting, but it doesn't deal with some of the surprising and fun things paint can do. Color theory is a limited approximation that works with light, but not really with paint, because in paint there are no colors, there is only chemistry.   And that's a good thing.   Pigments are chemical substances chosen for their optical properties, but they are more than just their optical properties. And you can do a lot with them. Any two colors can be blended