<p>The inner surface of a stainless steel water heater can undergo color change after a certain period of usage. The effects on the potability of water stored in such a water heater are unknown. In this study, to ensure the safety of public drinking water, the root causes of color change were analyzed through optical microscopy, scanning electron microscopy, energy dispersion spectroscopy, and x-ray photoelectron spectroscopy. Furthermore, the corrosion resistance of the color film was characterized through potentiodynamic polarization and electrochemical impedance. From the results, we can conclude that the thickening of the oxide film at higher temperature caused the color to change to purple on the top of the water heater, which is above water level. Furthermore, the scale attached to the bottom, which prevented the passivation of the stainless steel surface, caused the color to change to yellow on the bottom, which is under the water level. The overall corrosion resistance of the color film in tap water is not as good as that of the initial passivation film. This work provides a reference for the color change analysis of water heaters and helps prevent the recurrence of similar failure.</p>