When I got them they were all quite pale and assumed they were all I thought Leucistic's, this wild type colouring has developed as they got bigger.
Would have no idea what specifically to class them as, but do love the colouring and have only ever had dark Axolotols exhibit the same spotted colourations.
Gravel - understand I will never get any approval off the forums regarding gravel in the tank. For me I use the finest gravel I can find and never feed them on the gravel, not had a problem ever in probably 10 years now, and is just my preferred tank environment.
That being said juveniles and young Axolotls I will raise in a bare bottom tank until they are of a decent size.
I posted to see what people thought of the colouration, not for another gravel discussion.
=)