The TomTom wirelss GPS guide can be downloaded here:-
http://www.tomtom.com/lib/doc/ttwirelessgps_uk.pdf
But to answer your question-
4. Indicators
Bluetooth Indicator
The left indicator shows that your GPS receiver is switched on. Whenever this indicator is lit continuously or flashes, your GPS receiver is on.
The indicator flashes when it is ready for connection with your PDA, Smartphone or laptop. If there is an active connection between the GPS and a device, the indicator will be lit continuously.
When the battery level is low, the indicator will turn red, meaning the GPS receiver needs to be charged to guarantee continued operation.
GPS and Charge Indicator
The right indicator flashes continuously whenever the GPS receiver is determining your position ("getting a fix"). When the internal battery is charging the color of the indicator will turn red or orange.