To respond to the questions of the OP:
Every single race has a very large range of colors of skin, eye color and hair color that don't fit the norms we know in RL and some by way of small mutation which is widely accepted. Typically, as far as I am aware, racism of a different color of a race in Arm is actually frowned on because of the fact it too closely resembles things in RL. Racism in the form such as human to elf or half elf is accepted and thematic. As a caveat to this there is a wariness, hatred or dislike of Mutants such as someone with bark for skin for example, but this is more commonly found in Allanak. Mutants are pretty accepted in most other parts of the known especially that place with closed gates. At the end of the day, a human would see a human and same goes for any race. The only one that gets a little fuzzy now and then is a half elf who can sometimes be hard to discern immediately.
To the side question: I don't think I have ever personally felt that Zalanthan humans are based towards a "White culture" and I believe the game as a whole has been very good about keeping RL notions like that out of the game. Zalanthan humans are Zalanthans and come in many shapes, sizes, colors and so on and many with small mutations(despite most males being amazingly buff looking). There are the city humans, tribal humans and the mix of in-between. Based on all these examples of colors and differences I think you could very well play and write up a Zalanthan any way you want that fits within the documentation.
As a final aside to another post I saw in this thread, there is already scalping IC and has been for quite some time.