How are blue eyes adaptive?

What about people whose eyes change color? My sister had blue eyes as a toddler, but brownish/hazel by school age.

Then she started out with very little melanin in her irises and more was deposited as she aged. That is not an uncommon thing, for babies to have light colored eyes that darken.

As this article, which describes this, notes, it takes until a baby is about 2 years of age before their eye color reaches its final shade.

My older daughter had some pretty crazy steel grey eyes before they turned brown.

Doesn’t have to be linked - early European Western Hunter-Gatherers were dark skinned and blue eyed.

Not necessarily - at least one cite says green eyed.

Although he was WHG, so clearly there was variation there.

There is Lola as well.

New Hampshire’s DMV would consider this hazel because they change colors: when I specifically asked, they made me correct my renewal form’s stated eye color. Like yours my eyes are most often a grayish blue-green but at times clearly blue or clearly green- and my license now says hazel.

Huh. That’s not how I have every understood the word “hazel.” I thought it meant green with bits of brown in it.

That would mean that my eyes—which are gray if you actually take a photo and use the color-picker tool—would be considered hazel, and not the usual blue.

In fact, I would think that would eliminate anyone who had “blue” eyes. As blue eyes are always just some sort of gray. And gray always changes apparent color depending on surroundings

Ehhh, I’m not so sure about that. Gray/Hazel eyes end up changing color because their color is neutral enough to have their appearance changed by simultaneous contrast. For instance, my wife’s eyes are usually gray. But if she cries or her eyes just get irritated, they will appear green. My eyes are a dark blue, and the only way you’re going to get them to appear as another color is to view them in very low light where they will start to appear black.