My first instinct is to say it's mostly that photo.

Keep in mind lessers and butters do vary greatly in coloring. Some being very cream and others yellow. I've seen adult examples of both, and I think it mainly depends on the individual snake.

My husband picked up a very deep yellow lesser male as a baby, and as he grew he stayed ridiculously yellow, but he faded and blushed like all lessers do. He was incredible to see. We ended up keeping his most stunning daughter, and sold him.

If he does look like that in person, there is a chance he's something more than lesser, if you can get a few more pictures in different lighting that would be helpful.

Gale