Not valid....
Regardless, I'm going to probably keep using the Chingiss Khaan spelling, except maybe sometimes when quoting text that has the Genghis spelling or such (it will at least be in the quoted text, if not my discussion of it), so you needn't bother correcting me--just letting you know.
There is a legend of Chingiss having had red hair, promulgated by at least the Persian historian Rashid-al-Din (1247–1318), who never saw Chingiss, and the oral history of the Borjigid clan:
No accurate portraits of Genghis exist today, and any surviving depictions are considered to be artistic interpretations. Persian historian Rashid-al-Din recorded in his "Chronicles" that the legendary "glittering" ancestor of Genghis was tall, long-bearded, red-haired, and green-eyed. Rashid al-Din also described the first meeting of Genghis and Kublai Khan, when Genghis was surprised to find that Kublai had not inherited his red hair.[15] Also according to al-Din, Genghis' Borjigid clan had a legend involving their origins: it began as the result of an affair between Alan-ko and a stranger to her land, a glittering man who happened to have red hair and bluish-green eyes. Modern historian Paul Ratchnevsky has suggested in his Genghis biography that the "glittering man" may have been from the Kyrgyz people, who historically displayed these same characteristics. http://en.wikipedia.org/wiki/Genghis_Khan
Historians have been known to get a lot of things wrong. I put more weight on the genetic evidence, though even that is not certain, and the general appearance of the people alive today who are believed to be genetic descendants of Chingiss (though they would also have inherited genes from others, so a broad overview of Chingiss' descendants would be better if we had access to such), such as apparently this fellow, who looks like a Kazakh to me:
And this boy is a Hazara, who are a people that claim to have Chingiss ancestry and scientists did find the alleged Chingiss DNA among them:
I actually think it would be pretty neat if Chingiss had had red hair and shared relatively recent (say within the last 10-20,000 years) DNA with Europeans. After noticing many similarities between the horse cultures of the Mongols and the Irish, I wondered myself whether there might be a relatively recent DNA link and looked into it, but I learned that Chingiss' believed patrilineal haplogroup is C3, which is not one of the European (
http://en.wikipedia.org/wiki/Human_mitochondrial_DNA_haplogroup#European_haplogroups) or even proto-European haplogroups, AFAIK.
From this image, it doesn't look like C3 would be closely related to the "European" Y-DNA Haplogroups (R1b, R1a, I, E1b1b, J, G, N, or T--http://en.wikipedia.org/wiki/Y-DNA_haplogroups_in_European_populations), except perhaps E1b1b (which is found mainly in North Africa, the Horn of Africa, West Asia, and Europe):
I was mildly disappointed. If you come across any genetic evidence to the contrary, please do share it. Perhaps there's a link just a bit farther back then what I've found in my searches, or on Chingiss' mother's side (mitochondrial haplogroup).