You might look up the term constructional apraxia. Drawing using color is far more complicated than simply using black ink on white paper (like some cartoonists do). The ability to use color can extend into many different shades of colors. Snow White and the Seven Dwarfs had over 400 different colors as I recall. In my view, some persons may look at art a little like paint by numbers. The main thing is to create a picture, say of a dog, with many parts to it. Later the parts can be numbered for colors and the colors added. I know of one artist who tends to paint very simple objects (like a snow cone, a pie, rabbit, and so on). He tends to start with a white canvas and then using yellow to outline everything in a way. He said the yellow color made him happy. His final pictures have all sorts of colors to them - he paints over the base yellow.