Colorimetry is a commonly used color measurement method that can be used to determine the color value of purple beet.

1. Prepare the sample: Prepare the purple beet sample into an appropriate extraction solution. Purple beet samples can be soaked or extracted using appropriate solvents (such as ethanol, water) to obtain the required pigment solution.

2. Standard curve preparation: Prepare a series of standard solutions with known concentrations, which can be prepared using purple beet pigment standards or reference materials with known concentrations. Each standard solution should have a different concentration to cover your desired measurement range.

3. Colorimetric determination: Use a photometer or spectrophotometer to measure the absorbance of the standard solution and sample solution at a specific wavelength. Common wavelengths are the ultraviolet spectral region or the visible spectral region.

4. Draw a standard curve: Draw a standard curve based on the measured absorbance value and the corresponding concentration of the standard solution. The standard curve should be a linear relationship between concentration and absorbance.

5. Measure the sample: Use the same measurement conditions and measure the absorbance of your purple beet sample solution at the same wavelength.

6. Calculate the color value: According to the sample absorbance value and the standard curve, use linear interpolation or extrapolation to calculate the color value of purple beet pigment.