The new (circa 2002) 20 dollar bills that is siginfied by the pink and blue ink which has been added to the usual green and black. Due to the "flamboyant" color scheme of the newly circulated bills, the term "rainbow" was given to the twenty dollar bills. Not unlike the term "big face twenties".

the whale tail is the shape formed when a g-string rides up high over a womans trousers