This species actually comes from deeper water so my hunch is that lower not more intense light would be beneficial if this is the driver. That said I already run very low lighting (so low that my blastos have been reaching for light and they love low light). I would have to give up corals to go much lower.Most of the pictures posted on this thread do not show the deep rich royal purple and gold color that grammas have when they first arrive in the LFS. Maybe it is just the lighting, but most look faded to me. Everyone immediately jumps to diet, but I would not underestimate the effect light intensity and spectrum of the sun compared to our tanks as a possible explanation. I have generally found that high intensity lighting improves the color of the fish.
You could also argue it's less the light itself and more the stress from being in higher light than they naturally prefer. I've certainly not ruled out stress or other factors and I'm also adding more hiding places to see if that does anything.