Newman doesn't play an indian, he's a white who was grown up by indians, so that he thinks like them. So, no problem with his blue eyes.
I like this film very much. Ritt's best film.
And a great charismatic performance by Newman, often without playing.
But all the acting is great in this film (especially Boone).
Another fascinating point is the photgraphy (by James Wong Howe) and especially the often breathtaking use of landscape. You'll never find locations and images like this in a SW.
My only complaint is the sometimes a bit pretensious dialogue.