Blind blunder

My sister-in-law Mandy has always wanted to adopt children. She makes a strong case for why families in South Africa should. It's curious, though, that upon visiting the orphanage to play with some of the kids there, my nephew Asher made his request: "I want a brother like me... a lighty like me." Thinking he meant "laaitie" - a term of endearment for a male who is young or little, my brother pressed the issue. Asher responded by indicating the skin on his face, "not a darky one a lighty one like me!" Fortunately, the crowd of mostly brown-skinned adults laughed generously at the innocent blunder.
I wondered where and how he learnt to tell the difference: if by nature children cling to what is familiar and are hostile to what appears different, or if even at aged 3, he has perceived the differences in our society for brown or pale people...