Video/sync input connector pinouts:
Your red, green, blue, and black wires are the red, green, blue video and ground wires respectively. The white wire is the horizontal or composite sync input.
Now you also have a big problem with those large gauge wires that were cut going from the flyback transformer to the neckboard. That white wire is the "focus" voltage going into the tube socket on the neckboard. The red wire is the "screen" or "G2" voltage going to that gray single pin connector on the neckboard. Somebody cut those for a reason: maybe the flyback is bad and those wires were cut so it would get replaced. Maybe somebody simply didn't know what they were doing and cut the wires and didn't need to.
Here's what you're going to need to do before powering that monitor up: splice those flyback-to-neckboard cut wires back together again. Here's where it gets tricky. Those wires have high voltages on them so you can't just splice and wrap with electrical tape. The Focus voltage "white" wire has typically 8,000 volts running in it!!!!!!!! The Screen voltage has 400 volts.
Strip the insulation of the white wire ends about 3/8" back. With needle nose pliers, form the bare wire ends into hooks and hook each wire together. Squeeze snug with the needle nose pliers. Now solder the joint. After the freshly soldered joint has cooled (abbout 15 seconds) go ahead and swab the soldered surface with isopropyl rubbing alcohol to remove the solder flux. When dry glob on a bunch of clear silicone glue till the glob is at least a 1/4" thick and extends 1/2" on each side of this splice. Allow to dry 24 hours before powering up the monitor.
Do the same with the screen voltage red wire.
Your picture also shows the vertical yoke connector with nothing plugged in. Should be a connector with green and yellow wires on it goes there.