[jrumbut]

Funny, I still get the illusion after turning the pigeons every color from dark grey to bright yellow.

Brighter colors make it a bit less strong but still very much there.

[Enginerrrd]

On my laptop, I am only able to see the illusion if I looked at the striped background and blur my vision a little. Then it is quite impressive and strong. Otherwise, it always appears perfectly smooth for all colors.

[daveslash]

I get the illusion for yellow, but not for bright red or blue. That's interesting....