I'm on my second chocolate. I find the light pink is when he is at ease and the darker colors when he feels fiesty and is getting all whipped up over food. This second one is a bit more dominant in the tank than my first but shows the full range of colors. He never sulks but once late at night I turned the light on and thought he was dead. sort of just floating on the bottom with lack of color and striping.
I love these guys. Lost my first to a gash and then a huge infection. So had to get another.