The color of a diesel fuel is not related to its performance. As long as the fuel meets specifications, it will perform well in your engine. The natural color of diesel fuels has traditionally varied from colorless to amber. As refinery processing of the diesel fuel increases to remove sulfur the color has tended to get lighter and the diesel can change color. When it changes color the diesel is typically light in tone and can be green, orange or pink. Sometimes it might show a slight fluorescence when held up to light. Such a change in color does not affect the quality of the diesel.