Probably wasn't a Unix release per se, but the GUI you happened to use,such as raw x-windows (which would be my guess). There were other GUI's layered on top of x-windows, and it wouldn't surprise me if there were GUIs predating x-windows.
Initially, as I'm sure you know, Unix was solely a console-controlled OS. So the first color available would likely ...
Depends on what you mean by "OS support".
Early Unix (and all other OS) used video terminals that replaced the teletypes of even earlier Unixes.
These video terminals started supporting graphics and a bit later also color graphics. The first color graphics video terminal from DEC was the VT241 with Regis and Sixel graphics from 1983. BTW, Sixel ...
If you want to get it running on a modern Posix system, here's what you can do.
Get the source from this archive. (This is a more recent version than the one cited in the other answer.) Follow the instructions to obtain the files bsearch.c, Makefile, etc.
In smiley.c, there is a function explain, which looks like this: