A butterfly with four open wing panels floats among three daisies, and every panel and flower center holds an addition problem. The key at the top pairs four sums with four colors: 6 is red, 8 is orange, 12 is blue and 14 is green. Ten problems in all, and each one lands on one of those four numbers, so a sum that is not in the key is a signal to go back and check.
That self-checking quality is what makes color by number worth the ink. A child who colors two wings different shades has found their own mistake without anyone marking the page. The line art is clean and open, which suits crayons or markers, and it prints black on white.