I think I’ve mentioned one of my favorite watercolor tips in the past, but it is worth repeating. When mixing colors it is best to let them pool beside each other, just touching, instead of mixing them together with your brush. By laying them side by side on your palette you will get a more natural blending of the colors. Load your watercolor brush with the color that has swirled together to create the shade you are seeking. The samples below are my attempts to create natural looking greens. The watercolor shades I used are: Prussian Blue, Winsor Yellow, New Gamboge, Quinacridone Gold & Burnt Sienna.