Part of this story I'm writing involves a human subspecies who are adapted to extremely high altitudes -- as high or higher than our real world's Tibetan population, let's say. I've done research that indicates that the Tibetan adaptation to high altitudes in part involves either a decreased red blood cell count or a dramatically reduced amount of hemoglobin. I'm not sure if those terms are synonymous (I'm guessing they are), but sources agree on it being related to the EPAS1 gene. Anyways, I'm thinking about using the same mechanism for this population, although since they live higher up, and they've had a longer time to adapt, I assume they would have a proportionately more intense version of the Tibetan adaptations.
What I want to know is whether a significantly reduced red blood cell count, across this population, would be visibly discernible in their blood to the unaided eye, and thus what color their blood would be relative to lowlander red blood. Would it be less vibrantly red? More so? I initially wanted blood as vibrant as red paint, but I'm trying to be realistic.
An absence of sources detailing Tibetans having differently colored blood, to me, points to them not having differently colored blood. And I suspect blood color would vary more with degree of oxygenation than it would with cell count.