Let's select one of these paintings and simplify the shapes like we did for the monochrome studies, only here we'll copy the colors as nearly as we can. Use as many colors as you please. As an example, in the first image on the right side, there are three different groups of trees, two tall ones and one short. If you have made all three the same what would be an economic way to correct that? As you can imagine, this exercise will benefit from using lots of practice paper.
That's it. Pay attention to your technique. Do you adjust the color temperature or the hue to correct your colors? How do you lighten your colors? How does adding the compliment of a color change the mixture? How do you avoid running out of colors? Have fun!