The colour of something is the appearance that it has as a result of the way in which it reflects light
Hence, grass is green because when all the lights fall on it, it absorbs all except green, and so, we perceive green. A rose is red in the same manner and the VantaBlack and our eyeholes are black because they reflect almost nothing.
A good mirror simply reflects back whatever light hits it. Therefore, the mirror will take on the color of whatever light strikes the mirror.
If you have pink walls in the rest of the room, then when you look in the mirror, you will see the pink walls. Therefore, when you look toward the mirror, you will see the color pink. Therefore the mirror looks pink.
If you repaint the walls green, then the mirror will look green when you see the reflection of the walls in the mirror.
Well, if you throw white light on it, it will reflect white, hence, can we call it white?
Note : Copied from different sources