Last week I did an activity with the kids to teach them about colors. All you need is a box of fruit loops and some string cut long enough to tie into a necklace. Bub and Lou were old enough to "get" the color thing but the it was also good for the little ones' fine motor skills to try to string the cereal on the string and everyone had a great time snacking.
(This would be a great place to add an extra activity. You could prepare 3 glasses of water in clear cups. Mix drops of primary color food coloring to make the secondary colors appear in the glasses. Or do the same with white frosting. Or mix primary colors of paint to make secondary colors on a piece of paper. Any of these ideas would serve to reinforce the idea of mixing primary colors to create secondary colors.)
Happy learning, crafting and eating!