You don't want it. Most servers have it disabled, and may ban you for having it turned on.
Outdated information is outdated.
A few versions back, Badspot put a limit on avatar changes to one per second, effectively breaking "Rainbow Player" script. (Since it constantly changes the player many times in a second, and now it can't.)
Attempting to use the script now will just make you change to seemingly random colors once a second, and have people laugh at you if you say why that is.