Hello there! I've seen your posts about using the fog light plug to add lights. We are customizing a 2013 ST by adding underlighting. We have a non-spyder kit, 12V, with positive and negative wires to hook to the power source. The fog light plug has 3 wires, numbered, 1 gray with red, 2 black, 3 gray with green. Do you know which of these is positive? Is it safe to assume that black is negative?