From X-Plane SDK
Red and green are used for normal vector rescaling - see PluginsAndObjects for more info. Blue level controls the flash speed. Alpha provides a time offset to flashing.
RGB color is set to white. Alpha is set to brightness or 0 for off.
This light turns off when runway lights are inoperative.
The object sequence number can change the phase of this light.
The wigwag light modulates its brightness based on the angle the user looks at it -- it will go dim if viewed too far off angle above, below, left or right. The RG components rescale the normal. The "direction" of this light is always along the Z axis (subject to animation).
The wigwag light also pulses on and off - the color controls the timing.