Nine Purple Dots
I posted this little optical illusion yesterday on BlueSky and it proved so popular I thought I’d repeat it here.Whichever of the purple dots you look directly at turns more purple:
I find the effect is stronger on a smaller screen (e.g. on a phone).
In a nutshell, this happens because your eyes have reduced sensitivity to blue light at the centre of your field of view so the purple (which is a mixture of red and blue) changes hue if you look directly at it. For more details see here and the following blog post:
I’m interested to know whether or not this works for people who are colour blind, so if that is you please let me know!
In the Dark 
June 8, 2026 at 10:28 pm
@telescoper.blog witchcraft!
Not colour blind, but this is cool. Thanks for sharing 😊
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