The tank looks awfully dark with that blue background so I would add in a light colored substrate. Also I would add in some hiding places for him just in case he feels a need to hide. A fish that can't hide will become stressed eventually and have its immune system compromised because of it. It's better to have a healthy fish that hides rather then an unhealthy one that can't. But generally I find that if a fish has an abundance of hiding places it won't feel a need to hide all the time just because it knows it can hide if need be. Another practice I use is to use a mirror for about 15-20mins after feeding. This helps keep em fiesty while also boosting their color development and kok growth. Think of it this way, if he's got nobody to show off to or be aggressive towards he'll be very bored and have no reason to show off his colors.
