Does everyone see colours the same way?

Inside our eyes there are tiny cells that catch light. These cells sense colours and send a message to our brain. Our brain reads this message and shows us a colour. Because everyone's eyes and brain work a little differently, two people looking at the same apple might not see exactly the same red.

In some people, the colour cells are missing or work differently. This is called colour blindness. A person with colour blindness might mix up red and green. It is not an illness, it just means the eye senses colour in a different way.

Scientists even say this: even two people with the same kind of eyes might have brains that read colour a little differently. So the 'blue' you see and the 'blue' your friend sees might not be exactly the same, but you both call it 'blue' because that is what you learned to call it.