At the end, the green circle had a very intense grainy, hypersaturated quality for me. Not like the shimmering aura that shrinks with the red circle, but still there was something magical going on.

I looked away, and then back to the screen, and the effect was gone. It was only in my head. Wow.

A super fun, delightful experience indeed.

I, too, had this view. It was flecked with blue. Like a linen sheet it had those lines.

To my eyes, it looked like TV snow made up of blue and green particles! Twas quite delightful.

I had to zoom in to double-check the blue dots weren't there!

I looked away, then back, and the effect was gone—but then reappeared after a second or two, only less pronounced.

The one with a red circle on a brown background had a really interesting effect; before the circle starts to shrink, the background becomes the same colour as the circle, then moving your eyes made a bright red or green circle appear, each on their opposite side.

I got that, as well as a seemingly random set of changes in apparent brightness. The Magenta one seemed to produce patches of bands in my vision as well, think like blown up versions of edge detection kernels.

Do you have red-green color blindness ? The background is clearly green.

Edit : Apologies, I just now see the other ones.

To me, it seemed to be a visual equivalent of that auditory trick where a note seems to descend or ascend in pitch indefinitely. The outer aura of color seemed to be shrinking constantly.

The Shepard Tone - https://en.wikipedia.org/wiki/Shepard_tone - brilliantly used by Hans Zimmer in the Dunkirk score.

You can also look at the background about halfway through and get a large circle of the new color, the same size as the original circle.

The aura was a very brilliant green, which reminded me of an hallucinogenic experience I had. I was sat with friends in the city centre, my brain altered by chemical substances, and I spotted a guy 100m away with the most brilliant and beautiful green shoes. It was an amazing sight, standing out from everything else.

Sober, I later realised that they were normal green shoes, but in my no-brain-filter state, I was able to appreciate that we have many more green cones in our retina than red or blue, and normally the mix dial for green in our brain is kept pretty low not to overpower the other colours. The animation once again raised this dial to show how powerful is our raw perception of that colour.

(The evolutionary reason is that we spent a lot of time in vegetation or on trees, and it's very useful to be able to distinguish things and perceive small movements in a sea of green.)

Yes, this reminded me of a similar experience camping with friends where we could only describe the foliage as “ultragreen”. An incredibly vivid blue-green tone that suffused the whole island where we were staying. Been looking for explanations since

Ultragreen is a great way of describing it. That's exactly it.

As the circle was about to disappear, the blue-green was super saturated for me and persisted for a good minute if I kept locking onto the white dot. Another thing you can do, is at night time (lights off) look at the red circle like before, and when the timer runs out close your eyes and keep it dark. You will see blue-green glow very strongly.

Same thing for me, although, it looked more like an aura rotating around the red circle with a cyan-ish glow with a hint of teal.

Similar, an extremely bright and magnificent teal-ish green with a vibrant yellow edge was dancing around the edge of the circle

Serious pleasure