Malcolm is obsessed with Elmo. He is also very fond of coloring. I tried to use this to my advantage and a while back taught him colors according to his beloved sesame street characters. He caught on very quickly that red="elmo", yellow="big bird", and blue="cookie".
Malcolm is also stubborn. Although he now understands perfectly what "red" means, he refuses to say it himself. I've gotten a few strange looks while grocery shopping as I nod and affirm his pointing to blueberries and saying "cookie". Luckily, he's not a fan of Oscar the grouch, so "green" is the only color he'll consent to saying.