Inside Earth by Poul Anderson

The biotechnicians had been very thorough. I was already a little undersized, which meant that my height and build were suitable -- I could pass for a big Earthling. And of course my face and hands and so on were all right, the Earthlings being a remarkably humanoid race. But the technicians had had to remodel my ears, blunting the tips and grafting on lobes and cutting the muscles that move them. My crest had to go and a scalp covered with revolting hair was now on the top of my skull.

Finally, and most difficult, there had been the matter of skin color. It just wasn't possible to eliminate my natural coppery pigmentation. So they had injected a substance akin to melanin, together with a virus which would manufacture it in my body, the result being a leathery brown. I could pass for a member of the so-called "white" subspecies, one who had spent most of his life in the open.