To my only-moderately-trained eye, it looks like a transitioning Caribbean bluehead wrasse - but it could be lots of other things I'm less familiar with.
There's actually a long thread here on R2R all about identifying wrasse, and the pros tend to monitor it:
Got a wrasse but have no idea what species it is? Post it here with a good, Email me: [email protected] with a clear picture and I'll ID it for you. If you can capture a photo with the fins flared out, all the better. :wink: And go!