Why zoas thrive, but the color is gone ?

[road102]

Hello
How can I have bright green in my gsp, lettuce coral and mushrooms but not in this colony?. When I bought the frag they were just a few little tiny zoas but they had a bright green/yellow ring that is now almost gone.

Here is a reference picture I took from google that is showing the ring I remember they had.

My colony is the one in the red circle

 

[Lavey29]

Lighting or you bought a different species