The color of mineral oils can vary depending on the quality of the oil, its aging state, level of contamination or specific production processes. Color determination can be used as a tool to detect undesirable changes or contamination in mineral oils, but a change in color does not always indicate a problem. Some additives or manufacturing processes can affect the color of the oil.

Common methods used to determine oil color:

**ASTM D1500:** This is a standard test method for determining the color of mineral oils. Specifically, it is a test performed using the Saybolt chromometer. This method involves comparing the oil to a specific set of color references.

**ASTM D6045:** This is another standard for determining the color of oils using automatic color measuring devices. This test measures color using a spectrophotometric device.

Oil discoloration can be attributed to a number of factors, including oxidation, thermal stress, excess water, or the presence of other contaminants. However, in some cases, the discoloration does not affect the performance of the oil. Therefore, it is important to evaluate color changes in conjunction with other oil analysis results.

Also, the color of a particular oil may be different when compared to another brand or type of oil. Color is not an absolute indicator of oil quality or performance, but when used in conjunction with other analyses, it can provide useful information.