don't try to do a finished piece, just play..there is a book called blue and yellow don't make green, i have never read it, but wish i had a copy i always remember that red and green are best friends so are blue and yellow purple and orange try red and green first..the green will neutralize the red, setting a proper shadow color..it takes very very little, and a bit of experimented. I am so stubborn that when i started to paint, even tho i had read this a dozen times, i would reach for anything BUT the color i was suppose to use. Then one day i did, and omg..it worked! I taught Aaron this by using food colouring in glasses of water. We drop by drop added colour to experiment..it was a fun thing to do with a child..you can do this with anything like coloured pencils to watercolor..just mix in a tiny tiny bit, test it on a scrap and see what you think..have fun! I but never use black.....ever. The closest i will get is dark burnt umber which is colour i adore because it mixes without turning to mud. i like to add a bit of red to the pupils and that seems to puff life right into my little guys.