The internet is losing its composure over this dress that might be white and gold or black and blue

[Scootaloo]

26. Yup

Focusing on the dress, your brain sees the overall murkiness of the picture, and tells you that you're looking at white anf gold, in shadow. But then you notice the background, and it's not in shadow, so now the actual color of the dress - blue and black - comes out.

it's an interesting little thing that demonstrates that nothing you see is real. Now that may sound kind of woo-woo, but... it's true. Every shape, color, image you see... is imagination. The colors and images you "see" are actually just how your brain is interpreting electrical impulses that are generated by photons hitting your retinas at different speeds and angles. You have no guarantee that the stuff you are seeing is actually as it appears. Thus the old thing about how your red might not be MY red.

This is how all optical illusions and facial simulacra work; if you saw what was actually there, you'd never be fooled by them. but since what you 'see' is really just your brain trying to interpret electrons pinging around, your "vision" can be fooled pretty easily.