I think after so many times of reporducing they get slight variations in colors,size. But lighting also has a direct affect on the color of a zoanthid.
Well, non-scientifically speaking, I morphed 3 times when the right amount of alcohol was added. It seems to be a delicate balance of too little or too much though...
I say lighting. Those of these went from t5 to LED
Rose Nebs got a blue tint in their skirt. Space Monsters got some yellow in their skirt, also notice the two smaller polyps that are doing their own morph. IMO, it's all due to lighting.