The general definition among herpers for T-positive albinism is any mutant gene that is both recessive to the corresponding normal gene and seems to have some melanin but less than the normal amount. By this definition, coral glow/banana, lesser, pastel, and many other mutant genes are not T-positive albino genes.
I think that the recessive to the corresponding normal gene criterion is irrelevant. As far as I can tell, its only benefit is to keep the T-positive albino group of genes from being unmanagably large.
I generally ignore the T-positive/T-negative terminology. They are meaningless buzzwords. They make us think we know more about the biochemistry than we do, and they are totally artificial groupings. Besides, there are no proven T-negative albino snakes. The corn snake's "T-negative albino" mutant gene (AKA the amelanistic mutant gene) is now known to actually be OCA2-negative. As mating an amelanistic corn snake to a "T-negative albino" rat snake produces albino babies, the "T-negative albino" rat snake is also OCA2-negative instead of T-negative.
For example, in boas Kahl albino and Sharp albino are both classed as T-negative albino because neither produces melanin. Sharon Moore caramel is classed as T-positive because it produces some melanin. However, nobody has done the work to determine whether any of them directly affects production of the tyrosinase enzyme; possibly none of them do. The Sharon Moore caramel gene and the Sharp albino gene can form a gene pair, which means they are different versions of the same gene and part of a natural grouping. On the other hand, the Sharp albino gene and the Kahl albino gene cannot form a gene pair. They are not different versions of the same gene and not part of a natural grouping.
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