IBM 6C4 - Manual (Page 29)

Component LEDs
Individual LEDs are located on or near the failing components. The LEDs are located
either on the component itself or on the carrier of the component (for example, memory
card, fan, memory module, CPU). LEDs are either green or amber.
Green LEDs indicate one of two things:
v Electrical power is present.
v Activity is occuring on a link. (The system could be sending or receiving information.)
Amber-colored LEDs indicate a fault or identify condition. If your system or one of the
components on your system has an amber-colored LED turned on or blinking, identify
the problem and take the appropriate action to restore the system to normal.
The following table identifies the location, color and status of your system component
LEDs.
Chapter 2. Using the System 11