You see yellow when you cover the blue light. Red and green light makes yellow. Do you find that strange? Then you probably learned to mix colours with paint. But mixing light works differently to mixing paint.
How do you actually see all these colours? Tiny cones, located inside your eye, are responsible for this. There are three types: some cones are sensitive to red light, others to blue or green light.
Depending on how much each type of cone is stimulated, you see a certain colour. If all three are stimulated equally at the same time, you see white.
Colour vision of birds
Birds have 4 types of cones. That’s how they can also see UV light. Something that we, as humans, can’t see.
Colour vision in case of colour blindness
Some people are colour-blind. They do not see all colours equally well. This is because one or more types of cones in their eyes do not work (correctly).
Colour vision of bulls
Believe it or not, bulls are not at all angered by the colour red. They only have two types of cones and cannot see red at all!