If the owner thinks it is an Axanthic, and I personally do not by the way, then the easiest way to prove it out is by using an Axanthic to breed it to.
It is obviously not an Albino, but using an Albino mate would at least give you Albino Hets as offspring, and by the off chance it is an Axanthic, you could make Snows-which is why I think the one poster said to use an Albino.
It looks more like a burgundy type Hypo to me, I would say not an Axanthic.
Dave