The only real way to tell true axanthics from grayish colored normal is ventral scale coloration. If the ventral scales even have a hint of yellow coloration, they are not true axanthics. Also, at hatchling/juvenile size, true axanthics should not show brown coloration on the dorsal.

Here is a true recessive axanthic.

And a JMG co-dominant axanthic/Arctic. This is the non-super form. When 2 of these are bred together, it produces super which are black and white.