Using the photo you took home, or one of your own, paint a simplified version using only one set of primaries to mix all the colors. Choose any red, yellow and blue, and stick with that set. You can switch to different primaries on the next version. Have fun with it. This is more about color mixing than it is about making a painting. In fact, it is NOT a painting. Take your time with the colors, but don't correct the paint application. Let the mistakes show, take notes, and make another version. The second one will take half the time of the first.