Has a role in the biogenesis of eye pigment granules. Eye pigment granules are specialized forms of late endosomes or lysosomes. Biogenesis of pigment granules in the eye requires molecular components required for protein delivery to lysosomes. Expressed in eye pigment granules. Expressed throughout development, highest expression being in adult heads. Flies exhibit defects in vesicular transport to lysosomes and therefore can alter eye color. Pink was the second eye color gene identified by Morgan and colleagues, mutant flies were isolated in June 1910 just 2 months after isolation of the first white mutant allele. Another mutant allele of pink, peach, was isolated by Bridges in 1913, and according to a review published by Bridges and Morgan 10 years later, these alleles represented the first case of multiple allelomorphs described for an autosomal gene in Drosophila. Belongs to the HPS5 family.