Once an SPS has turned for the worse, in my experience, it's difficult to bring it back. It's not impossible though. I've seen them recover after measures were taken to facilitate recovery. It's no easy task, by any means, to bring one back.
It's hard to tell in the dark picture. Agree with both PhaneSoul and studda - If it has its polyps and flesh, it can come back with a lot of effort on your part. Do the polyps still have color (zooxanthellea in them)?
Oh yeah, there is tons of color there (of course color in white light is better, color under blues is a good sign) . Good water quality is a must as well as any other basic sps care. Ive brought back 2 sps (one was a digi) from being electrocuted on accident, the digi was bleached out and now 2 months later im seeing growth to him and good color recovery. Good luck!
I received this rock in shipping of a macro once. Took about 8 months to get to this point in the photo, otherwise now it's a bright purple tissue with green polyps.
I glued it to that frag because I recall someone saying 'hard corals never REALLY die!' heh..