Astatotilapia latifasciata color question

I just picked up 7 adult zebra obliquidens at my lfs. The problem is they all turned out to be male. I added some younger ones from another breeder hoping there are some females. The thing is, all look normal except one. He looks just like the others when he was bagged up but once I added them to my 120 gallon tank he darkened right up. His stripes are darker and his head is solid black now. I took some pics at the link below. The first three pics are of him in a separate tank showing less color. Pics 4,5 and 6 are of him right after I added him back to the 120. He instantly went black again. I thought he was displaying dominance but he is not the dominant zebra in the tank. Any thoughts? I'm not sure if its dominance or if he may be something else. I dont think so though since all 7 adults came from the same breeder. But I think he does look pretty cool. Pic 7 is of one of the other adults to show what the rest look like.
http://raff.shutterfly.com/action/s...b0de21b3414d0a450a&auto=1&m=1&d=1211255454460