Sherwin Williams uses a spectrophotometer to match paint color formulas. The company's proprietary color matching technology, known as Sher-Color, takes both the base color and sheen of the sample object into account to produce a highly precise color match.
Spectrophotometers are used in colorimetry, the science of quantifying and describing human color perception. The machines measure the visible region of a color sample and place it on a spectral reflectance curve, producing a highly accurate profile of a color.
Sher-Color spectrophotometers are computerized and can match a color from nearly any object an individual brings into a Sherwin Williams store. Some examples of objects that the company's website cites as replicable include rugs, pillows, fabric swatches, or swatches from a competitor's paint line. The system only requires that objects be at least the size of a dime, be of a consistent color and finish, and be non-porous.
After applying the Sher-Color system, Sherwin Williams provides customers with a custom tint formula, which is printed on the lid of the paint container. The company also logs the customer's custom tint into its computer system and stores the information for six years. This allows a customer to return to the store and easily replicate her custom paint color in the future.