I have always felt a bit uncomfortable using food to make art. I cannot help but to cringe and think that we should be eating our produce, not printing with it. But, I decided to go ahead and spare some produce for the sake of art the other day. You want to use tempera paint for this. Cut some interesting fruits and vegetables and set out some paper (we used a huge sheet of newsprint). Simply press the friut or veggie into the paint, then onto the paper and repeat. We used primary colors and I did not impose any rules regarding which fruits needed to be with what colors. I let her just go with it.
I did not use much, half an apple, a strawberry, half a brussel sprout, a small hunk of red cabage and the stumps of a green onion and a carrot. The carrot was not very interesting, the cabage fell apart. The green onion and brussell sprout were beautiful and the apple was Hollin's favorite to work with. Peppers and mushrooms would also be fun to try. The objects do tend to get slippery with paint, making it a challenge for little fingers to hold, so try to wipe your child's hands (and the object) from time to time to avoid frustration.