If your talking about the wires that go from the power supply to the wall, yes that is the standard. The wiring convention is black is hot, white is neutral, and green is ground. In the EU brown is hot, blue is neutral and green with a yellow stripe is ground, the yellow stripe thing is fairly common in the US too.
Here's a useful refference: [
en.wikipedia.org]
My power supply isn't grounded, and is not polarized (IE you can plug it into the wall in any direction), so apparently it doesn't matter all that much.
