I definitely understand doing a couple drain and fills to put your mind at ease, but I wasn't too concerned. Everyone on the TacomaWorld forum says the factory fill on the front differential comes out looking pretty rough. Your GX460 has a fancy Torsen front differential, though. Mine is a simple open differential.
I would check your fluid after another 10k. If it looks fine, then it was just the break in. If it still looks bad, then start worrying.
I would check your fluid after another 10k. If it looks fine, then it was just the break in. If it still looks bad, then start worrying.