It is a kids cardboard picture book that each time you turn the page all the objects are in a different shades of a single color and one object is of a different color. There are words on the pages like rhymes that highlight the object that is of a different color (for example a gray umbrella among a bunch of yellow items). The title might have rainbow in it. On the cover I think there are circle cutouts that get wider and wider that hint at the colors featured.
It might have rainbow or colors in the title which was written in black letters I think in like a 70s curvy thick font