Sorry. Actually I answered that from memory. It is the right hand green that defaults to always on (viewed with the ethernet ports towards you).

Assuming we are actually talking about the AR300M…

The red is WiFi.

The leds seem to be named as follows:

gl-ar300m:system (green)

gl-ar300m:lan (green)

gl-ar300m:wlan (red)

and can be configured in Luci