The international standard since around the early seventies is:
Green with Yellow stripe: Ground. Safety connection between chassis, and audio ground and the power outlet earth.
Light Blue: Neutral. Mains supply, usually 0 volts, but don’t rely on it.
Brown: Active. Mains supply usually 240 volts or whatever, but don’t rely on it.
It is common for the active and neutral of power outlets to be reversed, so never assume that switching off the “active” wire makes a machine safe. For electrical safety reasons, *unplug* the machine – most power switches on power outlets only switch one wire.
The Green with Yellow stripe is easy to remember as ground. I remember that Brown is active because that is the colour of the dirt they bury you in if you touch it.
The old standard was:
However this was changed due to the high incidence of red-green colourblindness – many males (it is usually blokes) see very little difference between red and green.
As for the anomalous wiring on this TR-808 (mine has the Green with Yellow stripe ground wire) – I could hazard a guess, but I would prefer not to, in case the guess turns into a hazard.
The two alternatives are using a meter to check which is ground, or to pull the machine apart to see where the wires go inside.