^Yellow metal with purple polka dots?
.. Like Zappa & Beck meets Mayhem.
edit :
Ugh, according to wikipedia : "Unblack metal (also known as Christian black metal) is a term used in reference to black metal banRAB whose lyrics and imagery depict Christianity positively."
Maybe it doesn't take so much modification. Instead of "we aim our arrows at the throne of christ", you just scratch christ and replace it with Satan.