“I think the Wikipedia is reliable for the Buddha’s appearance on the origin of the Shakyas (Shakya - Wikipedia). It supports the Pali and Chinese early Buddhist texts:
“Origin
The Shakyas were an eastern sub-Himalayan ethnic group on the periphery, both geographically and culturally, of the eastern Gangetic plain in the Greater Magadha cultural region. The Shakyas were of ‘mixed origin’ (saṃkīrṇa-yonayaḥ) of Indo-Aryan and Munda descent, with the former group forming a minority. The Shakyas were closely related to their eastern neighbours, the Koliya tribe, with whom they intermarried.”
The historical Buddha very likely looks like vasala, caṇḍāla (領群特, 旃陀羅).”
It’s a meaningless idea, since there’s nothing that a vasala or candala “looks like”.
Candalas were corpse workers, and they existed all over India and Sri Lanka. They would have been no less diverse in appearance than any other group.
The Buddha’s family probably looked more or less similar to the people of the region today. In the suttas, people comment on the Buddha’s beauty of appearance, but no-one mentions that he looked unusual or different.
As a rule, skin color in the long term is correlated with distance from the equator, as melanin evolves to protect the skin from the sun. So people in the south of India tend to be darker-skinned than those of the north. But this is far from an absolute, because, well, people move around.
I don’t really think that one can infer from what somebody called a ‘Chandala’ in recent history looks like (even if there is some correlation between this status and a person’s appearance) to what somebody called a ‘Chandala’ 2000 years ago looked like (even if there was a correlation between this status and a person’s appearance).
My understanding was that the brahmins, on the whole, looked down on the samanas, seeing them as outside of the varna/cast system. So it only matters that the Buddha looks like a samana to earn this kind of abuse. To the traditional brahmin samanas were also outcasts.
