Looking for a rainbow trail

Basically what the title says, I’m looking for something that’ll make it possible to a dd a rainbow trail to objects and ragdolls.
Probably the wrong forum or something, but I wouldn’t know where to put it.
Help is appreciated, thanks.

Rated gaybow.

guessing you’re going to do that Nyan cat?

There is a troll trail. I guess somebody would redo it…