The Axanthic morph is what's called a Base morph. Meaning its a base mutation that was found in the wild and found to be genetic (transmissible to offspring)
The Axanthic morph is also a recessive morph (like Albinos).
If you breed a Axanthic to a Normal you will producing offspring who look normal but have a heterozygous(het) hidden gene.
So to make one you need to breed a visual Axanthic to a another visual (100% chance of producing visual Axanthics), a visual to a het(50% chance of producing visual Axanthics), or a het to a het(25% chance of producing visual Axanthics)