The color or colour of a beer is typically described using either the Standard Reference Method scale (SRM), Lovibond scale, or European Brewery Convention (EBC) scale, which reference a numerical value to define the color and shade, and in some cases clarity or turbidity of a beer. The higher the number, the darker the referenced color is.
A beer’s color is primarily composed from the pigments of the grains that make up its grain bill. The pigment of a grain will darken if it is toasted, caramelized, or roasted, and that will impart that color on the finished beer. In the case of an imperial stout, the roast of the malt is so dark that it makes the beer nearly black. It is important to remember that as the color of the grain darkens, the acidity typically increases. Beer can also gain color from adjuncts, such as fruits and sugars.
Below is an approximate SRM\Lovibond color scale: