hey guys i was wondering what the different colors are best for:
i also need a recomendation on which to use for an IAC motor.

they have
blue
black
gray
copper
......and more?

 

Red rules.

What are you doing to the IAC? Blue works well for most applications where exhaust heat isn't a factor. Goodluck

 

Blue is for water aplications.--resists heat and coolant
black is for valve cover gaskets and such, all around purpose
Copper has the mettalic count witch makes it for exhaust and high heat apps.

all i can remember