Question

Why we see black and boiler colour when we close eye

Answer 1

When closed, our eyelids are good at partially blocking light from entering the eye. This effect is more pronounced in dim environments (i.e., the darker it is outside, the darker it would feel with closed eyelids).

However, our eyelids are not completely opaque and, therefore, cannot block all light (and most definitely not powerful light sources, such as the sun) from entering the eye. In fact, you should NEVER look towards the sun for more than a few seconds even with closed eyelids, as you risk significant damage to your retinas (the light-sensing tissue at the back of your eye that allows you to see). The same is true for lying on the beach without proper covers for your eyes on a sunny day.

The reason you experience a red-sensation when looking at the sun with closed eyelids is your blood. What you are essentially seeing is a certain portion of the electromagnetic spectrum (longer wavelengths = orange/red) that is filtered through the blood vessels in your eyelids and cause you to experience a reddish-hue.

Answer 2

Because we see it for close