That said, periodic mutations for blue eyes probably happened fairly frequently. It's just that people in a lot of the world (particularly in hunter gatherer days) would be highly likely to die if they had blue eyes.
The reason is simple. Blue eyed people actually do have a harder time with bright sunlight, because the iris contains less melanin and thus filters out less ambient light. If you're a hunter-gatherer, having issues with sun glare could mean the difference between life and death, if you're chasing down prey or trying to avoid a predator/another tribe.
Do you have any specific proof for this? Because this explanation honestly doesn't make a lot of sense(especially given that not all hunter-gatherers lived in the tropics).
That doesn't explain blue eyes being found amongst populations in West Africa, however.In high latitudes, however, the issue would not be as dire, because for most of the year the sun comes down at an indirect angle, meaning light is dimmer. Apparently it was enough that blue eyes were fixed in the Mesolithic European population by the time that (lighter skinned, brown eyed) farmers from the middle-east began migrating into Europe.
That much is true, at least.Blond hair though is doable - particularly if it comes through a variant like in Oceania, where you can have blond hair and dark skin at the same time.