Do you see the same yellow?

A cream and yellow exhibit table and headboard with the title 'Do you see the same yellow?'. A black box with 10 lights in a circle sit on the table.

Due to differences in receptors (and genetics), two people can perceive the same colour as being different.

How it works

Look at a circle of ping pong balls illuminated by LEDs (light emitting diodes) so they appear ‘yellowish’. The middle ping pong ball contains pure yellow LEDs, while ping pong balls in the surrounding circle have different proportions of red and green LEDs to give yellowish coloured light.

You need to choose the ping pong ball in the circle that most closely matches the yellow ball in the centre. See if your friends or family match up the same yellow coloured balls as you.

Things to try or ask around the exhibit

  • Which coloured light in the circle matches the coloured light in the centre?
  • Do you ever have arguments with someone about the colour of things?

Background


Humans perceive wavelengths of light as being particular colour and we all differ in our colour perception, thanks to differences in our genes and trichromacy, which is the technique humans use to perceive millions of colours. Light receptors (or cones) in your eyes detect certain wavelengths of light and generate colour responses in your brain. So your brain ‘sees’ or perceives colour rather than your eyes.

You may assume that you’ve got a huge range of cones for all the colours in the world, but your eyes can only actually detect three wavelengths of light:

  • Light at around 480 nanometres is seen as ‘violet’ by your brain (detected by short or S-cones in your eyes).
  • Light at around 530 nanometres is seen as ‘green’ by your brain (detected by medium or M-cones).
  • Light at around 650 nanometres is seen as ‘red’ by your brain (detected by long or L-cones).

You can see so many more colours than just red, green and violet. And there are no ‘yellow’ cones, so what happens when you see yellow?

Light at 570 nm is interpreted by your brain as ‘yellow’ and mixing red and green spotlights creates light which your brain also interprets as yellow. Your cones which respond to 530nm (‘green’) and 650 nm (‘red’) wavelengths of light are both being stimulated when you see 570 nm light. Your brain combines the nerve signals from these two sets of cones and you perceive yellow.

Finding the science in your world

Because we all have slightly different genes, we also have slightly different amino acids called photo pigments in our cones. This tiny molecular difference produces differences in colour perception between people.

Some people are more sensitive to 650 nm (‘red’) light, while others are more sensitive to 530 nm (‘green’) light. This affects how they perceive yellow coloured lights that are created with a mixture of red and green light.