Technically, if the animal shows outward signs of carrying a gene, then it is NOT a recessive gene...it would just be a subtle incomplete dominant gene.

If it's truly a recessive gene, the animal will not be distinguishable from a normal. Albino is an example of a recessive gene. There are no 'markers' for het albino. You simply can't tell them apart from normals.

Now, don't confuse 'het' with 'single copy of a recessive gene', because a lesser platinum is a heterozygous animal. Heterozygous simply means it carries one copy of a mutant gene, instead of 2 copies.

So, a het red axanthic is Heterozygous for red axanthic. It could have been called a 'strawberry ball', or whatever, but alas, the discoverer opted for a less creative name.
Red Axanthic is not a recessive gene, it's incomplete dominant--just like Lesser Platinum/BEL. Lesser Platinum could have been called 'Het Blue-Eyed Leucistic', if that had been what Ralph Davis wanted, and it would be just as accurate as 'Het Red Axanthic'.