Here's another rather nice way to mess with your mind - but you'll have to prove it to yourself.

Question: What colour is the tile in the centre of the top of this block?

-O.K.-

Now... what colour is the tile in the centre of the front face?

 

Own up.
You said "brown" and "yellow" didn't you!
Actually, they are identical; uniform, selfsame, indistinguishable.

If the animation at left doesn't convince you (please excuse the limited gif palette, and the blips from the animation), then I suggest you copy the above picture into a graphics program and see for yourself.
You may view a more convincing (but big - 145k) version of this animation here.
Click to open this page in a new window Break out
of this frame.
Click to go to PHS home page