I'm pretty sure these two guys are Khampas, warriors from southeastern Tibet. the CIA considered funding their rebellion in the early 60s if I recall correctly.
Tibet is a desolate colorless plain most of the time, the people make up for it with brightly painted buildings and clothes. I'm not sure what was going on with the two in the second photo and their elaborate red hats - the townsfolk wore everyday clothes, while the pilgrims wore their best.
It was interesting looking back at these photos after I got home. The bus from Lhasa to the border was a three day adventure, and looking at the Lhasa pix I recognized quite a few of the people in the background who would later be on that bus - like the woman in the off-white sweater on the right