@Danpiker@mathstodon.xyz It REALLY seems to depend on the screen one is using. I first saw this using my desktop monitor and the purpleness of the dot was staggering. Now, seeing the same image on my laptop, there's almost no purple. If I had only seen it using the laptop, I would be convinced that the effect doesn't work for me. I guess the colour gamut of different screens is important for this illusion to work...