Mouth gaping on an anmeone can be the cause of so many things I can't list them all, some good, some bad. What you can do is simply examine your water chemistry right down the the last test kit on the market to make sure you are providing the best enviorment for it.
Now this is a 55 gallon with 265 watts of PC lighting on it right? In my opinion this is fairly week lighting for a LTA who's nature it is to be at the bottom of the tank. You are losing PAR the farther you go down into the water column. I'd rather see stronger lighting, at least double of what you have now. Also as your current lighting ages, that PAR gets weeker and weeker. Consider upgrading your lighting.
I know some keep LTA's with less lighting, and some of them seem to do ok, but more lighting is better IMO.
As to the color of the anemone. It does appear pale, as though the zooxanthellae is week within it. This might also sugest that the lighting is week as well, but then maybe you have not had it very long, least maybe not enough to tell.
So some questions from me.
1. Do you know the lighting that this anemone was kept under before you purchased it?
2. How long are you leaving your lights on now?
3. What are you feeding it.
4. Is the pedal disc in the sandbed right now?
5. Is the anemone lighter, darker, or the same since its been in your tank?
Thomas