http://www.pprune.org/tech-log/10181...-spelling.html
http://www.pprune.org/engineers-tech...ead-panel.html
If you pull a fire switch the systems on the affected engine (or APU) which will be cut off or isolated are those controlled by the switches on the lighter colored panels. In the 737NG it's Fuel, Electrical, Hydraulic fluid flow, and Pneumatics.