I'm not sure what, exactly, they're trying to say. They keep saying that the dots are blue, but all nine dots are purple (with color 7001FE, so plenty of red as well as almost maxed out blue), and they look purple. Am I missing something?

The headline is weird - it should be "which purple dot is the darkest?"

Unless I'm seeing something completely different than everyone else.

Still a really interesting phenomenon though

I only see purple dots. I can barely trigger the illusion if I scroll the page up and down rapidly.

For me they are all purple but whichever one I'm focused on is darker.

Okay interesting. At first I misunderstood the whole thing and then when I got it I didn't immediately notice it. But after staring (and checking with a color picker) I can confirm that there's a color difference of the other dots. But its really subtle at first and I didnt even notice it consciously.

Stop it