I just saw a picture of something similar to this used on shower tiles - it appears black normally, but goes through the color spectrum when it's between 60 and 90 degrees. I wonder if it would be good on a guitar finish. Maybe paired with some of those burnt "rainbow" metal humbucker covers..... :glasses10:
http://motostorm.com/gpage61.html
http://motostorm.com/gpage61.html