Originally Posted by Mindrunner

There's your answer, Maladaptive. Either that or once every fucking blue moon.

My guess would be: we'll occasionally see them in Step Up Gachas, in the final step: 33.3% chance at a Rainbow Dressbloom, 33.3% chance at a Rainbow Skillbloom (which will practically feel closer to 60%) and 33.3% chance at a blooming heart.