The color measurement test applies a colorimeter or spectrophotometer to evaluate the way a sample reflects or absorbs light. It is given in objective color values (L*a*b*, RGB, or absorbance) and is usually contrasted to a standard in quality control or compliance.

The color measurement theory is the quantification of the interaction of materials with light, either absorption, transmission, or reflection. It employs standard colour spaces (such as CIELAB) and devices (colorimeters, spectrophotometers) to code the visual colour into objective and reproducible data.

Color is a qualitative and quantitative measure. Qualitatively, it can be characterized by the hue, the saturation, and the brightness. It is quantified in terms of color spaces, such as L*a*b* or RGB, in terms of numerical values based on devices such as colorimeters or spectrophotometers.

CIELAB L*a*b* values are the most standardized units in the use of color measurement. These determine values of lightness (L*), red-green (a*), and blue-yellow (b*). The color differences between the two samples can be measured through ΔE.

The color may be quantified in L*a*b* (CIELAB units), RGB values, CMYK (printing), and ΔE (color difference). Colorimetric assessment measures also apply spectral reflectance and absorbance (A), particularly in liquids and solutions.

Color measurement methods involve visual approximation (against color charts), colorimetry (by means of filters and detectors), spectrophotometry (a more detailed spectral analysis), and image analysis by computer. These are color measurement methods that are applied in the laboratory, production, and quality assessment.

The measurement of color varies according to context in several units. Such common units are L*a*b* (CIELAB), RGB (Red-Green-Blue), and color difference (Delta E). In light absorption, there are no units assigned to absorbance. But the quantitative analysis of absorbance obeys Beer's Law in colorimetry.

Techniques of measuring color are visual color comparison, colorimetry (with colorimeters) and spectrophotometry (measuring spectral reflectance), and image analysis. Both techniques measure the reflection or absorption of light by materials and are commonly quantified. Therefore standardized in color spaces such as CIELAB or RGB.