In engine room, pipings in whole or a part of it's length must always be color-coded. Color coding of piping serves few purposs. One such purpose is to allow the engine personnel tell the type of medium flowing in the pipe. Another one is tell the temperature of the pipe...not "tell exactly how much the temperature is" kind of thing but to allow the engine personnel to know whether the pipe is hot or cold. Knowing the difference between them is of utmost importance.
Silver is used to paint the pipings where temperatures may exceed normal range that may cause skin burns should bare skin come in contact to such pipes...
Part of the fuel lines atop the heater is painted red while piping below or just adjacent the heater is painted silver...warning any personnel to take precautionary measures when going near the system.