IT SHOULD BE RED WHEN IT HEATS UP THE TYPE OF GLOW PLUG I USED TO USE BEFORE I CHANGED THE ENGINE FOR A TURBO 2.5 WAS O.S. NO 7 I FOUND THAT THEY WERE BEST FOR MY USEAGE YOU CAN GET THEM ON EBAY JUST TYPE IN GLOW PLUGS AND YOU WILL SEE LOADS OF THEM IT DOESNT REALLY MATTER WHAT ONE BUT I ADVISE A MEDIUM HEAT GLOW PLUG YOU GET AS LONG AS IT DOESNT SAY FOR TURBO ENGINES THEY ARE A DIFFERNT THREAD