HP-233Snf
Anytime you see a Green wire in a computer, (Personal Computer), power supply's ->power cable, it is for the Soft Power On function.
This way there isn't a cable, (Cord), going from the Power On switch to the power supply.
These are ATX style of power supply's.
The Black insulated wires are Ground wires. ALL of them.
There was a older power supply made, and this was the AT style.
To provide a solution, I'm going to give you some information on the power cables, for Both of these styles of power supply's, then some advice.
1.This is info, and photos of the older AT power supply's power cables,
http://www.playtool.com/pages/psuconnectors/connectors.html#oldpc
2.This is the newer ATX style power cable, and more specifically the 20-pin version,
http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20
Scroll down the page to view the 24-pin power cable, and then scroll down some more, to view the 20+4-pin power cable.
ALL ATX design power supply's use Pin 16 for PS ON, (Soft Power On), which is a Green wire, and ANY Black wire. ALL Black wires are a ground. Pin 15 has a Black wire, and is normally used to put a jumper in, from it to Pin 15. This turns the power supply on. There will be a small spark, and the chance of getting shocked.
What you are doing essentially, is using a personal computer power supply as a laboratory power source, therefore I cannot advise you further, as it is a Safety Hazard.