I have a small frag (3") that I picked up recently for $20, and it has the beautiful bright green polyps, but the base is dark brown. These were grown under natural sunlight at a coral farm down the road, literally, from me.
I'm hoping the purple base shows up soon. Here is an actinic closeup. I thought I had a pic of the whole frag, but I guess not.
The base looks purple here b/c of the royal blue LED's. It's really dark brown when the Phoenix 250 comes on.