Probably from the 1940’s or 1950’s.
It is about a white cat, probably a Persian, who is entered in a show. The cat gets out of the house and becomes painted with red and blue paint. The daughter of the owners says let’s take her to the show anyway and the cat wins first prize.
Could it be The Cat Painter by Becky Bravo?
Could be “Peppermint” by Dorothy Grider. Its a small tell-a-tale book and the cat is accidently dyed blue before a contest at school.