Colorimetric assays are laboratory techniques used to determine the concentration of a substance in a solution by measuring its color intensity. These assays rely on the principle that different concentrations of a compound will produce varying colors when a specific reagent is added. The intensity of the color can be quantified using a spectrophotometer, which measures the amount of light absorbed by the solution. These assays are commonly used in fields like biochemistry and clinical diagnostics to analyze samples such as blood or urine. They are valued for their simplicity, cost-effectiveness, and ability to provide quick results, making them a popular choice for routine testing.