Red is positive, green is the negative one. On the Parazapper Cca, 2 positives go to the foot pads, 1 positive goes to a hand hold, and 1 negative goes to a hand hold. It has the 30,000 Htz, and 2500 Htz...you can really feel it in the negative handhold when you switch it to 2500. I really thought it must be doing something when I first got it and put the negative on my liver on 2500--it felt like things were jumping in there (probably my poor liver)--and then found out it's not the thing to do.
Hmm, the ten dollar zapper I got off of ebay,(30,000 htz) doesn't have red or green, it's all black. Wonder if it would matter, or how you could ever tell which was which.