39:3-50 Color of Lamps: The color of light emitted or reflected by exterior lamps or reflectors on a vehicle shall be as follows... White when the lamp is a headlamp, spot lamp, or illuminates a license plate or a destination sign...Substantially white or amber when the lamp is a side-cowl or fender lamp, running board or other courtesy lamp, back-up lamp, auxiliary driving lamp, or a turn signal on or facing the front. Substantially red or amber when the lamp is a turn signal or stop lamp on or facing the rear.
So there you have it. In NJ at least, white turn signals in the front are legal; white turn signals in the back are illegal.