Colorimetric assays are laboratory techniques used to measure the concentration of a substance by observing its color change. These assays typically involve a chemical reaction that produces a colored product, which can be quantified using a spectrophotometer. The intensity of the color is directly proportional to the amount of the target substance present in the sample. These assays are widely used in various fields, including biochemistry, environmental science, and clinical diagnostics. They are valued for their simplicity, cost-effectiveness, and ability to provide quick results, making them a popular choice for routine analysis in laboratories.