Which socket for footswitch a 210RD??

My first post here so hopefully there'll be a little tolerance for my rather stupid question...
I did a really dumb thing, I have a 210RD (Model 210-RD-100, serial DP06920) and while cleaning it up I unplugged the reverb and footswitch units and didn't note down which plug goes in which socket. BOTH sets of sockets are on the UNDERSIDE of the unit. I rather assumed because the footswitch has angled phono plugs and the reverb straight, that they were kind of different. Mistake.
Anyhow does anyone know if the reverb is left or right (looking from back) set?

if you are looking at the amp from the back its red to the right ,black to the left,or red closest to the cab .hope that helps .

Thanks Bill, not quite because the 210RD has both the reverb unit and footswitch unit sockets underneath it - and I wasn't sure which pair of sockets was for which unit. However, I've solved it after Steve gave me a troubleshooting approach.
Looking from the back of the amp, left to right, it is:
- channel footswitch (black plug on my footswitch)
- reverb footswitch (red plug on my footswitch)
- red plug from reverb unit
- black plug from reverb unit
problem now solved