Taking a stab that wiring colour coding is pretty much the same across different models, according to the wiring diagram on the 400 there is a Brown/Blue wire from the right hand switch which is the 'Position' light (so live when switch is in either P or H position). Again according to the diagram this connects to a Brown/Blue wire in the loom and thence to the 7A Taillight fuse.
Don't know if things are the same for the 750 but it's one theory.