Ok i am by no means a expert. My experance with sun corals are from diving on the toki maru (WW2) shipwreck that was covered with them. the only time we were able to view the sun coral was at night when it came out to feed. It was a bright orange color. Very cool to see. during the day you couldn't tell they were there unless you got close. at night it was light the ship was a fire.