Wondering if he's changing colors or what?

[potatoking]

My guess is food stuff but I gave it a good rubbing and it's still there supposed it'll come off when he drinks but who knows

 

[SailBoat]

As a young parrot ages, some will change feather coloring. But that is normally when they are losing body feathers starting in late spring to mid fall.

Coloration of bills would be rare.