The rainbow bloon as a Bloon orignally appearing in Bloons Tower Defense 2.
Children
Zebra Bloon x2 (BTD4 )
Black Bloon x2 (BTD2 -3 )
White Bloon x2 (BTD2 -3 )
Parents
The rainbow bloon is child of Ceramic Bloons. Ceramic Bloons used to contain 1-2 rainbows. In Bloons Tower Defense 4 , the Ceramic Bloons have 2 rainbows.
Trivia
It changed its appearance several times throughout the series. In BTD2, it had a red "vertex", while in BTD4, it had a vertical "rainbow" pattern.
When an ice tower level 4 freezes a rainbow bloon, the rainbow layer pops leaving the zebra bloons frozen. This is the only way to freeze a Zebra Bloon.