Quel'Thalas was represented as blue/teal in WC3 and WC3: TFT, but that was by no means it's "canon" color in all of Warcraft lore. Just as Gilneas' color was black in WC2, but in WoW it doesn't really have that association, as in Gilneas City isn't predominantly black. You'd be hard-pressed to find a lot of orange in Alterac, either. Some of these colors are maintained in WoW such as Stromgarde's red, Kul Tiras' green, and/or the black of the Dragonmaw Clan structures (seen before the Horde refit of the Dragonmaw main village). Basically put, the colors in WC2/WC3 are more or less game devices that are sometimes honored and sometimes not, depending on how they want to represent the cultures in WoW - there's no real canonicity to them at the end of the day.