You can also tell they are the same colour by covering your screen where all the other tiles are (showing only tile A and B).
There is one I used to have where you had to find the black dot. I had it on my desktop for a little while untill it gave me headaches..
Its a black and white pattern, and wherever you focus on the white dots, the others a black. Focus on the black dots and they go white... very weird. Can never find that black dot .
How we perceive shades of colour depends a lot on the contrast from other colours around it. I used to have an illusion that made you see a colour that wasn't there. I'll have a look for it.
Homework for everyone next week!
No! I don't need to be reminded about school by "teacher" telling us to do "homework" Its to close the the end of summer break! I'm sticking with this illusion stuff and pretending I've got 3 weeks left!