Question

What are colours and why do we see them?

Answer 1

Roses are red and violets are blue, but we only know that thanks to specialized cells in our eyes called cones.When light hits an object – say, a banana – the object absorbs some of the light and reflects the rest of it. Which wavelengths are reflected or absorbed depends on the properties of the object.
For a ripe banana, wavelengths of about 570 to 580 nanometers bounce back. These are the wavelengths of yellow light.
When you look at a banana, the wavelengths of reflected light determine what color you see. The light waves reflect off the banana's peel and hit the light-sensitive retina at the back of your eye. That's where cones come in.