As said the diagrams arn't avaliable to the public for good reason as such most decent alarms wiring is black, the wiring is black so as it can't be identified, the labels are removed after fitting.

An immobiliser does as the name suggests and disables (Opens) when armed a circuit that will stop the car from running, a decent immobilser IIRC to meet cat 1 has to have two immobilsation points, starter and ignition for example, I personally would not interfere with the pump as if it did go wrong with the car running you could end up with a meltdown!

Gr may suggest ground but this is purely a guess!

M and M may be the immobilser.

Martin