What unit is used to measure the color of beer?

The Standard Reference Method (SRM) is the unit used to measure the color of beer, making it the correct answer. This method quantifies the color by assessing the absorbance of light through a beer sample at a specific wavelength. The resulting value allows brewers and consumers to have a standardized understanding of the beer's color, enabling comparisons between different styles and batches.

The Degrees Plato is a scale used to measure the concentration of dissolved solids in a liquid, which is more related to the sweetness and potential alcohol content of beer rather than its color. International Bitterness Units (IBU) measure the bitterness of beer due to hops, focusing on flavor profile rather than color. Color Grading, while it may refer broadly to categorizing colors, is not a standardized measurement unit like SRM. Thus, the SRM provides a precise and scientific way to quantify and communicate about the color of beer.