After some searching for images of lizard color patterns, I thought I would try a line of different colored scales down his side. Not terribly wide, but a variety of colors. The end result is probably more like stained glass coloration than I expected, but I think it adds some color to a fairly drab scheme.
He still leaves most of the color saturation on the base and with the rider, so maybe I'll paint the ornaments and see what I think after that. Teeth and claws still need color too, so that might start to make it feel more complete.