Color Convention for Power Wires

Red is correct for DC Positive but Black is correct for DC 0V by convention, not negative

For AC mains in USA/Canada Black is LIVE, WHITE is neutral, UK and other areas Brown is Live and Blue is neutral

LIVE

NEUTRAL

The only real consistent thing for pretty much all countries is Green, Green/Yellow or Bare copper is always GROUND

Now depending on cores and Voltages this all can change, also older wiring may be different, to be sure check local codes and WIKI https://en.wikipedia.org/wiki/Electrical_wiring seems to also have a reasonable list but verify local codes to be sure

So for DC Low voltages there is a sudo code (I doubt it is official), look to PC wiring etc for what I mean

Red - 5V

Yellow - 12V

Black - 0V

....

Red is correct for DC Positive but Black is correct for DC 0V by convention, not negative

For AC mains in USA/Canada Black is LIVE, WHITE is neutral, UK and other areas Brown is Live and Blue is neutral

LIVE

NEUTRAL

The only real consistent thing for pretty much all countries is Green, Green/Yellow or Bare copper is always GROUND

Now depending on cores and Voltages this all can change, also older wiring may be different, to be sure check local codes and WIKI https://en.wikipedia.org/wiki/Electrical_wiring seems to also have a reasonable list but verify local codes to be sure

So for DC Low voltages there is a sudo code (I doubt it is official), look to PC wiring etc for what I mean

Red - 5V

Yellow - 12V

Black - 0V

....

I take the path of least resistance and follow what PSU manufacturers do:

When a supply is asymmetrical, I use red for + and black for -.

When I'm dealing with a symmetrical setup, I use the same, but the ground point in the middle is green.

My breadboard uses the same convention:

Of course, then there's these :

The green/yellow was to overcome people with colour bindness.

Many people have the brown/green issue where the both look the same, and hence when brown is live and green is earth ... the result is not good.

Mark

Please be careful with the assumption that GREEN is the Middle because it is not, it is ground and only ground, it is possible that 0V may be tied to GND but should not be as assumption and with alot of electronics it is undesirable , in all of the above pictures Green is GND and not 0V, the one with Black as Ground goes against ALL convention and should be regarded as wrong or atleast very missleading

In the PSU picture it clearly shows that 0V can go as high as 240V above GND but no more, there will be MOVs etc to prevent it from happening but outside of that, the - and + are isolated from GND