To answer your question, there is no convention. They are used in Yaesu and other radios for power. As long as both sides are the same, that is all that matters. If you are only remaking one end, then you need to look at the cable colours and a wiring diagram to match it up.
If you connect a solenoid backwards, it will try to drive in the opposite direction.
The same polarity is recommended as a standard by RAYNET:
RAYNET-UK | Technical Team - RAYNET Power connector
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