Richie,
First, in the US and Europe, there are two totally different systems or approaches to standard colors for wiring, electronic and electrical. In electronic equipment, which usually includes vehicular and aircraft, black is typically ground or chassis or common or B- (if B- is floating as it was in some early radios like the BC-654). Green is commonly either filament or grid, more often the former in transformer operated equipment. Red and Blue are B+ and Plate. Etc. In electrical at least in the USA, black is the hot wire for 120 VAC systems. It should never be used for a ground wire. White is neutral. Green is ground. Red is the other 120 line color in 120/240 systems. I have seen green with a yellow tracer used for the ground wire in some European made power cords, instead of solid green. Don't know why.
Anyway, it would appear that the Chinese did not run ground wires around internal to the machine, although the wires are there. There really wouldn't be any need to as the whole machine would be bolted together. If one of the motors was mounted on rubber cushions or on swinging mounts or bolted to the bench separately from the machine, as is common with a lot of older US built equipment, then you would need to run the copper ground wires around. It looks to me like they used standard cordage and left the unused wires dangling. Not neat and workman like but not dangerous, either. Just confusing. I would first find where the other ends of all of the Gn/Y wires go but probably you could just tie all of them together and to a ground stud.
You are correct about the lack of a ground symbol on the inputs in the schematic. The schematic certainly wouldn't pass UL.
Robert D.
