Skittles is just a PUG formed from players from different factions. PUG is not the same as "skittles" because you can have a PUG formed from players of the same faction. The term is usually used in the context of CW/faction play where players from multiple factions form together in a PUG on a defense (and currently only possibly in a defense on the IS/clan border). Why skittles? Because the different factions = different colors of their faction logo = look like the candy. They're not always noobs because you can have experienced solo players in CW. And just because an attacking team comes from the same faction doesn't mean they're good or even well coordinated. So skittles defense can often beat PUG attackers.
Personally I think the term conveys nothing of value. There's nothing inherently special about PUGs coming from the same faction other than they're wearing the same faction color. Just my .02.
Edited by BlackhawkSC, 17 January 2016 - 07:10 AM.