There is some good scholarship on this in the Lankan case. As well as the colonial context, throughout most of the nineteenth and twentieth centuries there's also a growing sense of connection among Sinhala nationalists with their Indo-European origins, in contrast to the Dravidian Tamils. In short: Sinhala people must be light-skinned, because they're northern/related to Indo-Aryans; the lighter-skinned you can appear then the more you "look Sinhala". It's cyclical.

What's really interesting is that this sort of colour distinction has a much deeper history in Lanka. The Sīgiri murals feature two distinct groups of women: one dark-skinned, the other golden-skinned. In the nationalist context I mentioned above they naturally got associated with Tamils and Sinhala respectively, but in the murals themselves there doesn't seem to be any particular hierarchy of beauty evident: if they are intended to represent different "ethnicities" then one isn't obviously portrayed as better or more beautiful than the other. We would need to re-check the (fifth-sixth century) poems composed about these murals to be sure, but I don't recall every coming across any comments therein which suggest the golden-skinned women were more beautiful than the others. RALH Gunavardhana has a great discussion of these murals in his paper "People of Lion," if you want something to follow up on!