color tune lets you see what kind of flame you have in the cylinder you pull the plugs put this in place then put plugs back in it help to fine tune your fuel air mixture to timing if you have an orange flame you can adjust until you get a nice blue flame that will help the efficiency of the motor fuel burn and should be done when syncing the carbs i hope i explained this right i have the concept down but hard for me to explain its also hard to do on the 1st and 2nd gens without a mirror and some sort of adapter as there is not much room for this to be done