Abstract: The color changes of one representative FCC gasoline were studied. The red substance in the FCC gasoline was concentrated and separated by chromatography and analyzed by elemental analysis and gas chromatography-mass spectrometry (GC-MS). The main components of the red substance were found to be aromatic amines. Complexes formed from quinones and aromatic amines are the reason why gasoline being red, and acids can destroy the complex by reaction with aromatic amines leading to decoloration of red gasoline. A mechanism for the color change of gasoline is proposed.