Now that your sponge watercolor trees are dry, it is time to add the sky color. The trick to keeping the tree leaves looking fresh and colorful is to start with clear water around the edges of the tree leaves. Then paint in your sky color, starting from the outer part of your painting and paint towards the leaves. When you get to the clear water, tickle the color with your brush into the clear water to get it to make an soft edge. Don't forget to paint in some sky holes between the tree branches and leaves.
This is a fun exercise to do as a painting warm-up!