its the minstrel show
sometimes called harlequins
the degree of patchiness varies from, like a friesian cow to spotting and speckles
you need to maybe have a look at its siblings and see if any are carrying that colouration as they grow, might only be slight, like a toe of a different colour etc.
best idea is to breed back to one of these or either of the parents depending on sex, i know this may sound incestuous but is best way to fix the gene
axolotl genetics are very random and harlequins are rare and in demand overseas
i currently have young from a spotted female and golden male, with about 40 of the babies carrying the spotted gene in varying degrees, even some gold with black spots
good luck with babies and happy new year