Mine is growing quite quickly (about an inch per month, about 6.5" or so now). Mine was very light in color at first, and is now getting MUCH more vivid and dark. The belly was once white, and is now jet black. It is definitely the boss of my tank (there are other CA in there), but isn't aggressive, just very dominant. It's a voracious eater, seems to eat almost anything.
Here's an old picture of it, and I will take a new one in a minute and post it for you also.
Great species and highly recommended! My female grew from 4"-12" in a year. I have 2 other smaller ones and all do not bother anybody else. Here is the video: