I think the song is from an old Peggy Lee movie. Can't remember the movie, but the song goes (in part)

Red, and yellow, and pink and green, Orange, and purple, and blue, I can sing a rainbow, Sing a rainbow, Sing a rainbow, too.

Hope this jogs a memory somewhere because I've been singing this to my grandbabies but only know this one verse and would like to know the rest.