That same color scheme (common, uncommon, rare) has been around a LOT longer than WOW, they 'borrowed' it the same way a lot of other games have from other games that were around a lot longer than WOW. I am not sure who was the first, but that basic scheme has been in MMO type games for at least 15 years before WOW came out, going back to some of the text based MUDs (Multi-User Dungeons) of the mid to late 1990s