In the past guys have been wiring the front "T" to the harness coming from the driver side head lights. On a Model S the second wire from the right side of the socket is or should be red with a white stripe. If you tap into that, the front "T" will light up when the head lights are on.
I have had this wired to my Model "S" for years. The new RGB front "T" has to be wired to the appliqué to get the multi color lighting effect.
You can also just tie the RED GREEN and BLUE wire together - that becomes your ground. The WHITE wire is the hot 12 volt line and is connected to the headlight harness.
You can get a color generator and connect the RGB front "T" to it, then use the controller that comes with the color generator to operate
the front "T".