This is one of the most fun things you can do with that age group.

Make up games, anything is fun. Ask "Who is wearing a red shirt? (or what ever color shirt you have on that day, to demo the game.) I am! I am wearing a red shirt!" Then who is wearing blue pants? Wear is a green picture? Who has a yellow book? That kind of thing. You can also toss in adjectives. Who has a big red umbrella? Who has long black hair?

Another game to play is to have a student stand up and say the name of an object. They could say, "What color is my hair? What color is this pencil? What color is my book?"

Games like these are always very silly and a lot of fun, and sure to help the kids remember colors.

A third follow up lesson on colors is to ask them what things they have at home. "Do you have a cat? What color is your cat? Do you have a dress? What color is your dress? Does your mother have a bicycle? What color is the bicycle?" This helps them hear questions, hear a variety of nouns in sentences, and practice using the colors they've learned by applying them to everyday objects.

An assignment would be to have them bring in pictures of something that is red, green, whatever color.

Anyway, the best thing about teaching kids at that age and that level is that they love games, and the games can be quite simple to be fun and effective.