Since I'm sitting here with a voltmeter next to me, I'll point out that red==positive and black==negative.
The bigger point I'd like to make is that any talk of universal connotations of colors is probably wrong unless you've really studied it carefully.
For some history on why red means stop and green means go, see Straight Dope: http://www.straightdope.com/columns/read/437/who-decided-red...
Apparently it dates back to early railroads, where red meant stop, green meant caution, and white meant go. They discovered this wasn't failsafe when the red filter fell out, the train saw a white light and crashed. So they moved to green for go.
The bigger point I'd like to make is that any talk of universal connotations of colors is probably wrong unless you've really studied it carefully.
For some history on why red means stop and green means go, see Straight Dope: http://www.straightdope.com/columns/read/437/who-decided-red... Apparently it dates back to early railroads, where red meant stop, green meant caution, and white meant go. They discovered this wasn't failsafe when the red filter fell out, the train saw a white light and crashed. So they moved to green for go.