What Makes a Rainbow? is one beautiful book by Betty Ann Schwartz. Very colorful, beautifully illustrated, cleverly designed, and quite sturdy.
Primarily, kids learn about different colors from the book, but also they learn about different animals. Every page you turn features a color and the whole spread is washed in that particular color, highlighted with a strip of silk ribbon in the same color. (Oh, it's all about colors, did I mention that?) Each succeeding page adds a new color (so you get an additional strip of ribbon with each turn of the page) until you get all the colors of the rainbow. The last page of the book gives you a pop-up of a rainbow.
Initially I was worried that the ribbons might come out from the kids' pulling and tugging. Well, guess what? Our book survived both Josh's and Zoë's mighty tugs and it's still quite intact!
IMHO, a must-have in every child's library. :)