The primate research team of the Wildlife Conservation Society Galle (WCSG) has carried out research on Southern Purple-Faced Leaf Langur, and they are reporting that,

Twenty-six troops from rain forests and home gardens around Galle and Matara Districts have been observed during this study. While recording observations, the team found 30 individuals with unusual white colour morph in 14 troops.

The new colour morph was named as the Galanthus colour morph.

Galanthus colour morph was mainly observed among troops mainly from rain forest and rain forest associated habitats. Determination of genetic or taxonomic differences among the sub-species of these monkeys requires molecular and morphological studies.

Wildlife Conservation Society of Galle was established in 1993 in collaboration with the Maritime Museum of Galle. The society is registered in the Central Environmental Authority more via Facebook

The endemic Purple-faced Langur is the commonest larger mammal in Sinharaja Forest Reserve, located in Sabaragamuwa and Southern Provinces of Sri Lanka.Source

Thanks to Shivakumar Selvaraj for the tip.