I have three different Sarcophyton species in the reef. The first is a florescent green polyped variety. I have 2 frags of this from Cris (on RC) of the Rocky Mountain Reef Club. The top one is photographed with a digital camera and the bottom with a film camera, but the real color is a bright green like green star polyps. When closed it's totally white.

The next one is the variety usually referred to as Fiji Yellow Sarcophyton. It has a large Ctenophore, or maybe two that hides on the stalk by day. At night it comes out and sweeps the water with long feathery tentacles.
Note 9/20/03: The Ctenophores have reproduced. There are now maybe 8 of them, all on this sarc. People tell me they don't reproduce by division and it seems odd that they all found their way back to just this location. Maybe they were just very small to start with and I didn't notice them?

This last one is a super long polyped one. It came from Paul Ifkovitz.
In his tank the polyps are about 3 inches long. So far in my tank they are shorter, perhaps because of the brighter lights.