He may just be darker in color. He looks really good in the pic! If he seems dull, has a pinkish belly, and almost a silver sheen in the light, he's probably about to shed.
I think he looks nice.
Snakes vary in color in general. But they also change colors and dull out throughout a shed cycle. I suggest just waiting until he sheds to see his true colors, which is also the time they look the best.
Most photos you see here are of freshly shed animals.