I've seen my Jag in many different color variations. He's often the off white/cream color that you desire. Sometimes he turns more gold colored like yours but not quite as yellowy/gold. Right now he's really showing off his purple sheen and lots of blue on his dorsal fin to attract the female to mate. Unfortunately, she wants nothing to do with him. I don't know if yours will change or not. Try switching your substrate to a white sand and I can almost guarantee he'll lighten up some.