Dana Riddle has an excellent multi-part series on Coral Coloration. A good read if you want to know more.
He's done a lot on coloration, here is some:
http://www.advancedaquarist.com/2009/1/aafeature1
http://www.advancedaquarist.com/2009/2/aafeature1
http://www.advancedaquarist.com/2009/4/aafeature1
http://www.advancedaquarist.com/2006/9/aafeature
http://www.advancedaquarist.com/2003/11/aafeature
http://www.advancedaquarist.com/2006/11/aafeature2
http://www.advancedaquarist.com/2006/12/aafeature2
http://www.advancedaquarist.com/2007/2/aafeature
http://www.advancedaquarist.com/2007/6/aafeature2
http://www.advancedaquarist.com/2007/7/aafeature1
http://www.advancedaquarist.com/2007/6/aafeature2
http://www.advancedaquarist.com/2007/7/aafeature1
http://www.advancedaquarist.com/2007/10/aafeature2
http://www.advancedaquarist.com/2007/11/aafeature
http://www.advancedaquarist.com/2008/1/aafeature3