I have a powder brown tang. We've had it since November and it's done very well. It's a big eater and besides flake food, it picks at the algae on the coral and substrate (although it hasn't really made a dent in controlling the algae). I think he'd like dried seaweed, but I haven't tried it yet. Mine is rather shy, but it swims everywhere in the tank and is fun to watch. I've read that they don't like change and we haven't tried to add any new fish since we got him, so I don't know how he'll react to that. AFTER we got him, I read that it should be the last addition to a tank because of that...he won't be, so he'll have to learn to deal with it at some point.
We've been happy with him so far! He gets along with our clown fish just fine.
Not by any stretch of the imagination would I say there is any blue/purple tint to this fish. He is a brown/gray color overall, with white, yellow, orange and blue areas - but the blue is only a very thin line on the outside edges of his top and bottom fins. We got him because he was interesting and we hadn't seen one like it before.
As you can see, I had a little trouble with the photo post.
These are all the same photo, I couldn't see it had been added so I did it again...and again.
Anyway, sorry about the poor photo quality, he knows when I'm trying to take his picture and refuses to cooperate and slow down to a speed my camera can handle. But hopefully it's good enough for you to see the coloration and compare it to the white cheeked tang. (Anybody know how to remove extra images from a post??)