Yes t matters, the led with the red and black does not have a built in resistor. So if you hook it up to the +,- terminals going to the pump, you will cook it in short order. just ground the black and use the grey. My grey wire internally features a resistor just for this purpose. If you want to use the LED, you'll need to add a 1k ohm 1/4 watt resistor in-line with the red wire. And it may not reflect full brightness when the kit starts going.
Something trick is to connect a bulb across the +,- terminals.. then as the boost increases the intensity of the bulb increases. Typically on the GN, the bulb will be housed in the power injection hole of the dash. I never have had success using LED's to do this. Theyre brightness just doesnt change like a light bulb does.
HTH