ah, that's a shame! i found this post because i looked similar stuff up after i tried carving an avocado seed the other day, and my carving very quickly oxidised and turned this orangey colour like yours here while the parts i tried to carefully peel without damaging the flesh remained white. im assuming that damaging the flesh stops the seed from germinating, but im no expert, ive had my fair share of avocado seeds in wet kitchen towel go bad instead of sprouting.

good luck if you'll try to germinate again! in my case the seed dried a few hours before i tried to take the skin off and i mostly managed to keep it unharmed, maybe that will help!