"Part of learning about art involves understanding different materials, how they work and what you like as well as what you can afford. The 90 pound paper is very expensive so use it carefully.  Use some scrap paper for experimenting.  If you want to mix colors try to mix them on the paper.  For instance if you want green put some yellow paint on your paper, clean your brush and then put a tiny bit of blue on the yellow.  Try it either way yellow first or blue first.  Remember a little blue or red goes a long way on the yellow."