Place green beans and water in a microwave-safe dish, cover, and microwave on high for 5 minutes. (If frozen steaming may take longer.)
Meanwhile, dice red and orange bell peppers into small squares about the same width as the beans. Slice the yellow pepper into four pieces and then use a small star-shaped cookie cutter to make the star for each tree.
Cut cheese sticks in half.
Have your kids use the beans to form a tree shape. Use the diced peppers as ornaments and the cheese as the trunk. Finally, place the star on top.