I assume this is a 3 phase circuit, not a single phase one?
No. Black = hot, grey = neutral, red = ground. Old Austrian/German color coding. 3 phase would be even funnier. 4 wire 3ph systems would have been black-red-blue-grey, grey being either PEN or (usually) ground, others are phases. 5 wire is like single phase, S and T phase being blue and black (black-blue-black-grey-red).
