They act separate, but I'm not sure if that is normal behavior or if something is wrong with the yellow one. The yellow one just sits on the sand in a specific spot all the time. It responds to stimuli around it but doesn't go beyond that little corner of the glass, along the sand. I do see a green one occasionally sitting next to him, but no harm seems to come of it. Not sure if it is normal for them or if this one was too far gone. It doesn't act sick or dying though. Just like it has no reason to move.
The greens are all over the tank and interacting a lot though.
Sounds normal for the yellow's I always thought the other types were the same way, yellow stays perched in the rock only coming out for food.