Well, yes, but the point is, if they had no examples to follow, why would they choose that color? It would be just as arbitrary as if she chose to dye her hair blue or green.
And I concede that there are some people of other ethnic groups with reddish hair, but I don't know if we've seen any in the Avatarverse; and Ginger's overall look was just too much based on Hollywood starlets from our American cultural heritage, so it stood out as incongruous in this context.
While of course the show clearly has some very obvious influences from Asian cultures, I think it's a mistake to allow that to limit the scope of the show. Not *everything* has a direct parallel to the real world and not all the peoples seen on the show are 100% inspired by real world Asia.
For example, the swap water benders were decidedly not Asian. They were American hill-billies (or is it rednecks? I can never remember what the distinction is) with their design apparently influenced by South American tribal groups. The Sun Warriors also had a distinctly South American (Mayan/Aztec) influence while the sand-benders could be said to be at least partly influenced by Saharan desert nomads.
I guess what I'm getting at is that it's a big world and we've only seen a small slice of it. While it's clear the Asian inspired cultures are the dominant ones, for all we know there's a relatively small group of highland dwelling earthbenders with a thing for playing the bagpipes and a taste for koala sheep stomach stuffed with wheat and barley.
Besides, why would the show runners allow racial prejudice to get in the way of a good Jessica Rabbit joke?