What color is a mirror?

Mirror, mirror, on the wall, who is the fairest of them all.... That mirror in the story of Snow White was surely magical. But mirrors in real life are also special. Have you ever wondered, what is the color of a mirror? The color of a mirror obviously depends upon its surroundings. The color of an object which you view in the mirror becomes its color. This means that a mirror simply keeps changing its color according to the objects viewed in it. But most other objects normally don't do so. Then what is it that makes mirrors so different? To answer this question, we first need to understand what is a color and what makes things colorful.

What is a color?- Objects by themselves have no color. They simply reflect light falling on them. White light consists of all the colors or wavelengths in the visible spectrum. When a white light falls on an object, it reflects some wavelengths and absorbs the rest. The color corresponding to those reflected wavelengths becomes the color of that object. For example, a red apple is red because it reflects the wavelength corresponding to red color and absorbs most of the rest of the spectrum.

Case of mirror- By above logic, a white object is white as it reflects all the white light or entire visible spectrum falling on it. But then, a mirror also reflects the entire visible spectrum falling on it. Then how is a mirror different from a white object? Why don't we see images in every white object? The answer lies in the type of reflection taking place. There are two types of reflections- diffuse reflection and specular reflection.

Image by GianniG46 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11902338

 Diffuse reflection- In diffuse reflection, the incident ray is reflected in many directions rather than a single direction. It happens because of the multiple reflections taking place beneath the surface of the object. So, when some light finally comes out again from the surface, it can come out in any direction. The light coming to your eyes is a mix of light falling on the object from different directions and you can not see an image in such mixture of rays. This is what happens when you see a white sheet of paper. The light falling on it is reflected back but in different directions and because of this, the image is lost after reflection. In case of red apple, the light corresponding to red color is reflected in many directions and rest of the light is absorbed. So, you see an apple as red in color, without any mirror like images on it. But then how do mirrors work and how are slight images formed on other glossy objects?. This is where specular reflection comes into picture.

Specular reflection- In specular reflection, a ray of light from a single incoming direction is reflected in a single outgoing direction. This is what happens on very smooth surfaces and mirrors. The light rays remain organized,  image remains intact after reflection and this allows images to be seen. For example, if incident rays are parallel then reflected rays are also parallel. To make specular reflection possible, mirrors have a reflecting coating which is usually aluminum or silver.

Mirrors are different from white paper in the way they reflect light. Mirrors show images because of specular reflection while white paper is white because of diffuse reflection. And there are many other objects like glossy white marbles in which the effect of both types of reflections is visible.

If you still want to know the color of mirror, the answer is that it is slightly green. This is because most mirrors reflect green light better than other parts of the spectrum and this gives mirrors a slight greenish tinge.

So, specular reflection makes mirrors possible and diffuse reflection allows us to see most of the things around us. The mirror in your bathroom might not reply to your questions, as in Snow White, but we know now that it does have some magical physics working under the surface.

References-
https://www.rgbworld.com/color.html
https://en.wikipedia.org/wiki/Specular_reflection
https://en.wikipedia.org/wiki/Diffuse_reflection