No one knows the author.
Nobody seems to be concerned about the brazenly racial slant of the proverb.
One likely probability is that the idea could be a north Indian construct, something inherited from a quasi-Aryan bias against the native Dravidians of the subcontinent who were probably darker in texture than the erstwhile Central Asian and European brethren who overran the region. Samarqand o Bukhara ra. For him people living in India were Hindus after the River Indus that separated the two civilizations. Bereft of the ancient Indian Varna system from which the anti-black prejudice would seem to flow, there is quite a lot of civilizational affinity between India and Iran. But then that would include the dominant cultural elements of Pakistan as well, including language and religion.