So axanthic is a recessive gene, meaning two copies of the allele are needed for it to show in the animal (think blue eyes or blonde hair in people) while pastel freeways, which broken down are pastel, asphalt, yellowbelly, this means from pairing the two up you do have a possibility of getting more pastel freeways! But it’s much more likely to get single gene animals (only expressing pastel, asphalt, or yellowbelly) or a mix of the two, which still could lead to freeways since all the genes in a pastel freeway are codominant (only one allele is needed for expression, like brown hair or brown eyes). Either way back to the recessives, if you paired these animals you would not get ANY axanthics at all, instead all the offspring would be het (every single baby has one alelle) meaning they carry the gene, but only one allele so it’s not visible since it needs two. I’d advise against this unless you’re prepared to be caring for a bunch of heterozygous (single allele, what a non expressing recessive gene is, or a het) ball pythons that have a random roll at getting freeway or pastel freeway. Ultimately it’s up to you and your son, but I’d recommend studying morphs until you’re a couple years in and know the basics regarding what genes are co dominant and recessive, how genes work, and what morphs are out there. Personally I’ve only been keeping ball pythons for a couple years so I’m in no place to speak but they’re definitely fun to learn about.
Further on pairing ideas and explanation as to the probabilities in clutches whenever you pair what morphs your son has and wants to get with other morphs, if you have an axanthic, the main thing you want to pair it to is a het axanthic (one allele for axanthic, not visible) so that the babies have a 1/2 chance of being axanthic, while all the others will be het axanthic. The best possible pairing would be an axanthic to and axanthic so ALL the babies are axanthics (look up punnets squares and do a bit of research on them! Very good for “calculating” what you’ll get, it doesn’t really but it’ll show you what’s likely to happen, the morphmarket calculator for ball pythons is also very useful for calculating what offspring’s morphs may be) to add on TOP of that pairing an axanthic to an axanthic with co dominant morphs would add more variability and value to the clutch, adding recessives would not matter much, het or visible outside of axanthic since it will not show up in the babies unless both parents are het or visible, so adding genes like fire or champagne can be really fun! Co dominant genes have a 50/50 chance of being passed down to their offspring, so you’ll always have the chance of not only getting axanthics but some other morphs stacked on top for all the cooler and more valuable of snakes! As for the freeway pastel the best thing to pair her with if your son got her would be another snake with any CO DOMINANT genes only, the reason I stress this is because for a first clutch, from local sellers or friends having issues, you generally don’t want to be producing heterozygous recessive animals, since you end up spending more on a parent you sell the babies for less on, and it’s near impossible or is impossible to ID if a snake is heterozygous for something unless one parent is visible for the recessive gene in which case all the babies will be heterozygous, but you’ll still end up spending more on the parent snake. Definitely look into combos with the genes that make up freeway pastel that you and your son like if you end up buying an breeding her
Last final note on axanthics: there are different kinds of axanthic ball pythons so you’ll have to learn what kind of axanthic that ball python is before you pair them to any ol axanthic or het axanthic, and if you buy a het axanthic make sure it is ONE HUNDRED PERCENT het axanthic, not pos, 66%, or 50% since there’s the chance that it is not het axanthic and you’ll just produce a bunch of normals/hets if that’s the case
Another note on hets: there is one way to determine if a snake is het for something, you can send it’s shed in for genetic testing but it costs a lot (65 bucks each if I remember correctly?) and does not have every morph available for testing, plus you will not get visible morph ball pythons and I’m assuming your son wants to start out as a hobby breeder. Best of luck!
(I also recommend questioning regarding treatment of the babies after hatching, your son has to be prepared to take care of every single baby in a proper and good way like any animal should be, meaning, hopefully, how the parents are treated assuming the parents are also being well taken care of, you must have tip-top condition snakes for breeding that need tip-top care also, but after the babies hatch it’s likely they won’t sell right away, but also your son has the responsibility of making sure they go to good homes, the amount of times I’ve taken in “phase” pets is insane, people end up buying an animal from somebody who didn’t ask questions and they end up getting abused or dumped. So basically just make sure your son if prepared to care for up to a clutch of 16 babies, although that’s a very rare number, and treat them well as either keepers or until they go to a good home. Also keep market saturation in mind! The market it highly oversaturated so only breed the best snakes available!)