Apple AirPort Express 802.11n (1st Generation) - Manual (Page 11)

Chapter 1 Getting Started 11
When you plug the AirPort Express AC adapter into the power outlet, the status light
flashes green for one second, and then glows amber while it starts up. After it has
started up completely, the status light flashes amber until it is updated with new
settings. The status light glows solid green after your AirPort Express is properly set up
and connected to the Internet or a network.
AirPort Express Status Lights
The following table explains AirPort Express light sequences and what they indicate.
Light Status/description
Off AirPort Express is unplugged.
Flashing green AirPort Express is starting up. The light flashes for one second.
Solid green AirPort Express is on and working properly. If you choose Flash
On Activity from the Status Light pop-up menu in the Base
Station pane of AirPort Utility, the status light may flash green to
indicate normal activity.