false alarm lol. I believe that since the atlantic juvinile tnags on the interet are yellow i would say yes it is just some of its young colours slowly fading out. Theres me getting my pacific tangs and atlantic all mixed up
I have had mine for about 6 months now and it has only developed a thin blue line around the outside of it's dorsal fin and around it's eyes. It is just over 2 inches now. Here is a pic.
It was listed in our LFS as a juvinile atlantic blue tang. The guys in our LFS know us very well and they are very experienced so I don't think they would have listed it wrong.