1. The Rainbow Challenge capitalizes on children's natural love of color. Visit the grocery store or farmers' market with your kids, and challenge them to choose the most colorful variety of vegetables possible. You may want to set a limit on the number of veggies they can choose, or you'll wind up with a farmers' market of your own.
2. When you get home, provide your children with a culinary blank canvas (such as a tortilla or a whole grain pizza crust covered with some tomato sauce) and all of the vegetables they've chosen. If you're going to add cheese to the dish, do it now so the food art isn't covered up.
3. Ask your kids to make the most colorful, creative dish that they can, perhaps making patterns and pictures with the veggies. Encourage them to be imaginative; this doesn't have to look like any other dish they've ever eaten.
4. Bake these works of food art, and enjoy eating them together!
Take pictures of the vibrant dishes your children make. Make it a weekly game, and start a photo album or kitchen gallery.
When working with younger children, the grown-ups should serve as assistants by doing the cutting and cooking at their request.