What color does a red shirt appear when the room lights are turned off and the room is entirely dark?

Black

Explanation:

It is only possible to correctly visualize the color of a body due to the reflection that the light present in the environment. If there is no light and the environment is dark, no light will be reflected and we will see the body in black.

in other words, we can say that color is not a particular feature of the object, but rather a feature that depends on the light that illuminates the environment in which that object is.

When light hits a red shirt, that shirt absorbs all the colors present in the ray of light, except for the red light that is reflected in all directions. Without light in the room, there is no reflection, so the shirt is black.

Black

Explanation:

When the room lights are turned off any object present in the room appears black.