Purple, yellow, black, and white gave me all of these colors! Yellow watercolor looked "greenish" when I added black to it; yellow Posca markers also look "greenish" when drawn over india ink. (Tamas explained that this is a very desaturated yellow.) The odd brown spots on the fish came from mixing yellow and purple watercolor. This is maybe overly complicated but I learned a lot from the practice and decided to share what I learned with the rest of the students.  :) Please excuse the squares --I've just finished classes on Kandinsky & Klimt's markmaking and got carried away.