Is white usually positive?
The black wire is positive, the white wire is negative, and the green wire is the ground.
Is white always negative?
The color is always positive while white/black is always ground/negative. This is universal in most electronics except in home electrical where green is almost always used as ground. But red/green is positive and white/black is negative in your case.
Is white ground or positive?
Recognize that the black wire is the positive one, the white wire is the negative one, and the green wire is the ground. You may see a copper wire instead of a green wire for the ground.