I received many orders on rainbow butter cake that involves children. Actually this is a basic butter cake with colors added to it. It's very popular amongst children below 10 years old. I asked my nephew who is 7 years old, why he preferred the colored butter cake over the plain one. He said the colored ones taste better.......mmm, how colors effects children mind. There's one article I came across years ago said that, children prefer bright colors over subtle hues, their eyes not adapted to see dull colors, therefore they are partially color blind, something to do with their rods and cones not fully developed. Bright colors and saturated hues associated them with pleasant memories.