Teach colors with food coloring on your tongue!
Eleni's creative hack could dovetail nicely with the colored milk trick...
My niece is two years old and while she is learning to count (so far she can go from one to mawebban ) she has had trouble learning her colors. I bought a package of food coloring and every time I’d go visit Jaelyn and I’d use the food coloring to change my tongue a different color. I’d stick out my tongue and ask her, “Jae, what color is my tongue?” If she’d have trouble I’d help her out by telling her the color. After a few weeks she knew all of her basic colors and was looking forward to my visits more than usual. If nothing else it’s good for a few giggles. My nephew Aidan is 9 months and he loves it.
Now that's a devoted aunt.