What does spark plug color indicate?

[Marik123]

Recently I replaced spark plugs on both cars... 1 with a mitsubishi galant ES 2001 2.4L and other one is mazda protege LX 1.6L 2000. When I pull out the plugs from the galant, its in golden and tan color... I check that on the web, it indiciates its in normal operation. Then I pull out the plugs in the protege, the metal around is gold, but the materials around the firing tip is in dark red, what does that indicate? New spark plug is white. I replaced both cars with regular V-power NGK plugs... Car only ran for 15k miles, materials around the plugs turn dark red on protege? What does that indicates?

[SciFiMan]

Do a Google on "spark plug color" and you'll get some pages with pictures so you can compare. I don't know about the red color though....

[Marik123]

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

Mine is similar to #14, the materials around is red... But then how come when I press down the accelerator, my engine knocks? Isn't that relates to detonation or pre-igniation? Isn't red color means the engine is kinda hot?? My engine knocks when its under heavy load and driven after 20-30 minutes...

[Shane5425]

i know white carbon build up is from burning coolant, and black is from burning oil.. old plugs have a whitish dirty color.. red... maybe its too hot of a plug??? in my 3 years of auto repair , i have never seen a plug come out red....