Please don't request skins around here, this forum is to showcase created skins!
I'm pretty sure I've seen multiple rainbow colored skins around here, you could try
searching for one!
Also, you made
another post earlier, where you once searched for a rainbow skin and now wanted someone to make one for you. Please refrain from creating multiple posts for the same thing!
If you can't find a skin that suits your needs you could always just try to make your own, there are a lot of resources
here and
in the wiki with which you can start working on your own!