and only one of them can explain the skin colour (and everything else).
Nigel is wise to consider NO2. It is a a good candidate.after all there are many possibilities in the Dyatlov Mystery.
The poor autopsy reports and lack of toxicology report doesn't help. But there are obvious signs that some of the group members reported to have died of hypothermia didn't die that way.
I think it's accepted that only Igor clearly died of hypothermia, some clearly died of trauma (Semyon, Lyudmila, Nicolai and the rest are arguable - Yuri D - pulmonary edema, Yuri K - that he bit off the back of his hand and didn't have time to swallow it or spit it out before he died doesn't look good for a judgment of hypothermia, Rustem - weakened from internal bleeding he laid down in the snow - debatable which got him first, bleeding or the cold. Zinaida - cold would be likely but her bladder volume (300cm3) questions it and there is a good argument that she was too weak for the steepening incline.