xkcd

If you keep one eye closed and expose the other to sunlight, you can see the difference. The lenses tint a dark shade of purple. I have dark brown eyes, so you can't really notice the difference easily. There is a purple ring that is most noticeable outside of the limbal ring. They don't turn your eyes black like you had the tint of sunglasses or transitions glasses, which would be cool.

I would imagine someone with lighter color eyes, like really light blue, would have a very noticeable difference.

Something I did notice as the wearer is when the lenses are tinted there is like a contrast filter on your vision so colors look better.