HP ML530 - ProLiant - 128 MB RAM Setup And Installation Manual page 245

The hot-plug fan LEDs indicate the following conditions:
•
Green = The fan is operating normally.
•
Amber = The fan has failed.
•
Off = The fan is not installed, has no power, or is not properly seated.
HP ProLiant ML530 Generation 2 Server Setup and Installation Guide
System LEDs and Switches
C-11