1. Rubik’s illusion
The “blue” tiles on the left and the “yellow” ones on the right are the same colour.
3. Cube illusion
The upper grey cube and the lower grey cube are the same colour.
4. Crossed wires
The two crosspieces are the same colour. Also, the four angles are perfect right-angles on both images.
5. Brown noise
The “brown” square in the centre of the top side of the cube and the “orange” square in the centre of the shaded side are the same colour.
6. Orange is the new green
The “green” square in the middle on the left (marked with a black spot) is the same colour as the “orange” square on the right.
9. Lilac chaser
Stare at the center cross for 30 seconds to experience the illusion. You’ll see a green spot running around the circle, and the pink spots will fade.
11. Bright blue?
You’ll have got the hang of this by now, but the blue circles are all the same shade.
12. Dress (simplified)
Prof Andrew Stockman of UCL sent us this one. If you concentrate on the dark brown strips towards the bottom of the image, your brain will fill in the rest of them the same way, even though the higher ones are light: The reverse happens if you stare at the lighter orange ones at the top. (Confession: Only one of us can see this illusion.)
15. The Colour Wagon Wheel
Colour can also affect motion-based optical illusions – watch this video to see how altering colours changes how you percieve the direction the circles are rotating.