Are you talking about your emrald crabs? I know that some animals can change colors to the help blend in with their surroundings. Maybe emerald crabs can do this to some extent?
Ghost>crab<busters...
If there's somethin' strange in your tank
Who ya gonna call (ghost>crab<busters)
If it's somethin' weird an it won't look good
Who ya gonna call (ghost>crab<busters)
Gotta be the light. That 150 watt over the BC29 is a good amount of light. I've seen sps and lps burn and die if it was less than 6 inches from the bulb