No its not dyed the shops I bye from will not deal with fish that have been dyed and I've never seen a dyed fish in any shops over here, its not as blue as it looks in the pic more of a greyish blue but colour changed and became more enhanced in the blue when I adjusted the sharpness and colour in photoshop I didn't try to make it look unrealistic so sorry if it does.
Yeah, the levels tool in photoshop is probably the best tool for enhancing images, heres an enhanced pic of my eupterus