I have a taste of this when I got IOLs last month (cataract surgery). I now see colors I haven't seen in years. And I suspect that the IOL passes more blue light than my natural lens ever did, even when I was young.
I can see an extra shade of purple. I had essentially the same lens removal cataract surgery as Monet did. Like Monet, I can see slightly into the ultraviolet range, because the retina can react to some UV frequencies that the lens normally blocks! Unlike Monet, I'm not much of a painter.
It really does defy words, for obvious reasons. The short answer is that it's "like purple... but even more purple"
The slightly longer version is: imagine moving a color slider from red to purple and then keep going a little more.
From: https://news.ycombinator.com/item?id=44594808