We painted some heart cookies with food coloring recently, just for fun. We did this once before (painting directly on the uncooked cookies) but the colors were too dark and intense, so this time I diluted the food coloring with water (yellow and red) and milk (pink) first and think the colors worked out really well.
After cutting out the heart shapes from the cookie dough, I froze them so they would be hard and easy to handle while the girls painted them. They painted using q-tips as brushes.
I make these kids do art to get treats!
After baking the cookies, they admired their artworks briefly then ate them!
Note: We've also painted with food coloring on glazed cookies and glazed cupcakes. It's a very different look, but works equally well. And of course we decorate with icing and sprinkles. I've been really curious about the edible "Food Writer" markers, though. Has anyone used them?