My latest assignment* is to mix secondary colours from red, blue and yellow and use them exclusively in a painting (still life or landscape). So, just violet, green and orange. Adding a little white and/or black was allowed.
So far so good. Need to make a few adjustments here and there, and add some details (ie. the markings on the tape measure), but overall, it’s going pretty well. Learning a lot — which is the point, of course.
My reference photo: