Blue Jaw Triggerfish and pale blue jaw

So I have asked about this guy in the past (8 months at least), but I am going to ask again. My male Blue Jaw Triggerfish is about 4 inches and he doesn't really ever show off his blue coloring very much. Its mostly very light and hard to see at times unless you are looking for it. He dose tend to show it more when I am about to feed, but that's about it. Is there anyway that I can help bring that out? I feed Mysis, bloodworms, brine shrimp, scallops, store shrimp, green nori, red nori, and algae flakes every now and then. I figure its not diet since its pretty varied. I am out of ideas. He is very active and happy go lucky, and is always ready for his next meal. No one picks on him, he just goes about his business without a care in the world. The only thing I can think of doing to help bring out his color is add a female, but I don't know if that's a good idea in a 120 gallon. You guys got any ideas because I am at a loss? His personality makes up for is lack of color, but still, I would like to see the blue coloring that I know they are capable of showing. Thanks!