Axolotl getting much lighter and gills turning bright red

[Darfin]

My axolotl is acting normal and is still happily eating but his gills have turned bright red and his skin has turned from a dark black/brown to a sandy yellow/brown. Is this just a genetic trait being expressed late or is he sick? Pics below.

 

[michael]

It looks fine. Sometimes with a light colored substrate they lighten up a little.

 

[CarysR]

I know that sometimes dark axolotls will lose pigment in their skin as they age, making them lighter. Perhaps this is what's happening to your axie? It looks healthy to me.