Lol, that's been a debunked translation for a long time now but keeps getting passed around by western chauvinist.

"Perhaps the most well-known passage of relevance in Rashid’s work, is an episode where Chinggis meets his newly-born grandson Khubilai for the first time, and remarks that Khubilai lacked the red hair of his grandfather. However, that’s not quite what it says.

…when Chingiz-Khan’s eye fell upon him [Khubilai] he said: “All our children are of a ruddy complexion, but this child is swarthy like his maternal uncles. (Rashid al-Dīn/Boyle translation, pg. 241)

…when Genghis Khan’s gaze fell upon him [Khubilai] he said, “Our sons are all of a ruddy complexion, but this boy is swarthy, just like his maternal uncles. (Rashid al-Dīn/Thackston translation, pg. 415)

In the two main English translations by John Andrew Boyle and Wheeler Thackston, Chinggis specifies that all of his children are of a ruddy complexion, while Khubilai is swarthy like his maternal uncles. Ruddy does not mean red hair, but reddish face, while swarthy refers to darker, more tanned-looking skin.

In Rashid al-Dīn’s Persian text, he uses ashgharani اشقرانی to refer to Chinggis, and siyah-charda سیاه چرده for Khubilai. Siyah-charda is straightforward: it means black-skin. Ashgharani is a bit more complex. It comes from Arabic, where the meaning relates to blondeness. But in Persian, it has two primary meanings; a red-coloured horse, or a man of white and red features. Pale skin with red undertones. That is, ruddy. Given that the text directly references Khubilai’s dark skin, this must be the intended meaning. Certainly, Mongols and Qazaqs are prone to a certain reddishness of the face, particularly those exposed to steppe winds."