"My eyes are happiest when"...it really depends...

To use an extreme example, back when I was experiencing corneal erosions (you don't want those), contrast itself was the enemy. You send me this website, I am going to have to play with my display settings and also probably put on sunglasses.

Thinking of more common contextual preference change, time of day comes to mind.

I wish my e-reader clients could pick up on my time-of-day settings changes, because sometimes I want contrast and white on black, just dimmed in general, and at other times I want sepia but brighter...but generally there are obvious rules that could be derived based on what time it is.

(Sending people to websites like this without caging it in some kind of wink or chuckle of an expression seems like it would be a bit over the top...)

I totally disagree. My eyes ache after looking at white backgrounds too much. That's what dark styles are for. They're much more relaxing for me. I will never read a whole bunch of text if it's got a white background. It just plain hurts. In fact, I use a plugin that converts every page to a dark style. If there's a page that doesn't render well that way (rarely) and I really want to read it, I'll squint and read it quickly before I get some sweet relief by switching back to dark mode.

> The eyes are happiest reading dark text on a light background

Hi, dark mode-everything user here. I highly disagree. I don't have vision problems per se, but white everything at all times causes strain.

Also, comparing black vs light and vice versa for text reading is a bad example, but the author points it out by mentioning the changing of color schemes.

Edit: As a point, I'm using a moderate red color shift on my monitor on top of dark themes. It's far, far better for my eyesight than proverbially staring into the sun!