The implication that white is the most attractive exhibits white supremacy, where white is seen as the most superior. It creates a system of white supremacy in which white skin is valued above all the rest, invalidating the beauty and even humanity of those who are darker skinned through constantly ignoring their existence or misrepresenting them. Through colonization and slavery, white people were able to hold their status of superiority and power over people of color. The blatant unwillingness to have dark skin is a manifestation of the internalized racism carried within South Asian cultures, stemming from a past brimming with white supremacy.
Found a great article that discusses colorism in Bollywood.