I checked against the schematic V3 and measured from the audio connector's pins to the proper points on the components. The volume control wiring in your diagram is wrong. The green wire IS ground and connected to the proper point on the volume control as shown. The yellow and orange wires are switched. the pins of the connector from left to right as viewed from the front of the board are (verified with an ohm meter)
1 = microphone input - Purple wire
2 = microphone ground - Blue wire
3 = volume control ground - Green wire
4 = volume control high - Orange wire
5 = volume control mid (center) - Yellow wire
6 = ground - Red wire
7 = speaker high - Brown wire
8 = ground - Black wire
I have all of HF Signals version except Version 4. The above wiring is correct and unchanged on the 3 version 1 boards I have 116/1, 212/1, 324/1, 933/2 and now 133/5. I don't have either version 3 or version 4 boards but I hardly think the wiring to the audio plug would have changed for those 2 versions and then changed back in version 5.
The "Wiring Up" diagram that's currently on the HF Signals website has recently been changed and appears to be correct with respect to both the CW Jack and the Audio Plug.
Jim - W0EB