Does the color of the object being tested affect absorbance?
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We often measure the absorbance of paraffin oil, and paraffin oil samples vary in color – some are colorless while others have a light yellow hue. Does this difference in color make it impossible to compare the absorbance values obtained?
Yes, generally speaking, the yellower the color, the greater the ultraviolet absorbance, from what I understand
How can the absorbance of dark-colored substances be measured accurately, with the influence of color excluded?
For dark-colored substances, under normal measurement conditions, the absorbance is generally accurate； The influence of color generally cannot be ruled out; typically, paraffin oil is a mixture, and the various substances contained within have different absorbances (absorption coefficients). What is measured is the total absorbance resulting from the sum of these values. Pure substances with color generally have higher absorbances (absorption coefficients)
The colors that the human eye perceives are closely related to the absorption spectrum of visible light by a substance; of course, some infrared or ultraviolet absorption bands may also become apparent through certain color characteristics of the substance. Changes in the absorption spectrum of a substance or supplement can be determined by measuring its chromaticity, or by performing an absorbance scan of the substance within the ultraviolet-visible spectral range.