"Half Breeds"

Elvis is a "half breed" who has to choose which side he is on in Don Siegel's "Flaming Star" (1960).

EDIT: To give a partial answer to your question - about this particular movie anyway - Flaming Star is a plea for racial and cultural justice – a trend that was just beginning and went a long way toward establishing the movie industry’s status as “liberal.” At one point a character says, "It’s just plain hate now and everybody ready to kill anybody who isn’t just like him.”

ANOTHER EDIT: To bring Flaming Star up to date and make it more relevant, we might look at it like this - Although Pacer (Elvis) was born and raised in mainstream U.S. society, his ancestral ethnic identity lay outside “white” culture. Pacer is contacted by a terrorist leader from his ethnic heritage. The leader, who is very articulate and plainly sets forth some very legitimate grievances, wants to wage war on civilian society. Pacer, being sympathetic to the cause and because of other events, is radicalized and joins the terrorist army. But when the family who had raised him is put in danger, Pacer has to rethink what he is doing.

en.wikipedia.org/wiki/Circus_(1936_film)   --James Patterson was the biracial child. Interesting that this film was the prioritized social policy message around the time of the Ukrainian famine.

I understand that Cheyenne in ONE UPON A TIME IN THE WEST is described as a half-breed in some articles but I don't recall anything in the movie that supports it? Harmonica seems to be a Mexican or Indian based on the flashback of him and his brother.

Here's another distaff example - not from a western but an old school stage adaptation of a  revenge melodrama (THE SHANGHAI GESTURE)

The character of Poppy is originally depicted as a straight laced Colonial debutante enjoying an evening's slumming it at Mother Gin Sling's "Gambling House" (a whorehouse in the original play- and the sets in the movie are quite astonishing):

In the later stages of the movie - after she has discovered that she is half Chinese -  she is shown looking like this - her trollop levels increased immensely - now not at all incongruous to her surroundings:

Here's some of those sets

      

and here is Ona Munson as Mother Gin Sling herself

and here is Victor Mature in his best ever role as Omar the poet procurer

(Publicity still with Gene Tierney and Phyllis Brooks - who certainly seem interested in what he has to say)

Laurence Harvey as Biracial (Russian-Japanese I think) opportunist in A GIRL NAMED TAMIKO, planning to marry "fur coat no knickers" Colonial Club Princess Martha Hyer for the green card that will come with marriage.

 Must say he looks about as Japanese as Bugs Bunny , but aside from that he is well cast as yet another manipulative, unpleasant character... and the lush score and travelogue values are definite plus points, as is Hyer.

We will know that we have overcome racial prejudice when white actors can play Native Americans without causing resentment. As my dear friend BAT always says "It is called acting!"