Brushes that are trying to imitate pointillist (neo-impressionism) paintings. Usually there is a mix of two complementary colors in the paint layers when it comes to pointillism, but I haven't found a way to have exclusively those two so it is up to you.
Strong brush has a big difference in values, weak has a smaller difference (for painting skin, mostly) and water is for water ripples (duh). Have fun with those! As an advice, I recommend using complementary colors for shading to have that authentic neo-impressionist feel.
Brushes