Ed, I totally agree! The browner the faster they grow. The harder they are to kill, etc. I bought a huge zoa rock a few weeks ago, three different varieties, about 100 polyps that are brown skirted, grean with orange mouths, 40 that might be radioactive dragon eyes, and then there were about 12 that looked like eagle eyes or watermelons. They were the whole reason I bought the rock. Those 12 melted on me. All the rest, growing like crazy and even splitting off new little colonies.
Well, truth be told I really bought it becase the LFS had it mis-priced. Got all 150+ polyps for $30. But I'm still sad about the pretties.