The pink resistor wire limits current and not voltage. If all you need is a signal wire to turn on an ECU or MSD, the current is so low it will not drop voltage. There is a + wire to the battery that carries the load to run the ECU and/or the MSD.
It depends on the application. My FiTech and Petronix CDI has a wire that goes to the battery and requires a 12v switched power source for key on and crank. If you splice in after the pink wire, you won't get 12v.
If the pink resistor wire doesn't limit voltage, why do stock coils measure 6v to 9v at the coil?