According to the owners manual for these swimming pool lights
, this is what each colored indicator means. Hope this helps.
The battery pack is fully charged.
Slow flashing green
The battery pack is almost fully charged.
Slow flashing yellow
The battery pack is half charged.
Medium flashing yellow
The battery pack is less than half charged.
Fast flashing yellow
The battery pack has almost no charge.
Fast flashing red
A charging error has occurred and the light should be unplugged and then plugged back in. If the Fast Flashing Red persists after several attempts, the battery condition is questionable.
Also in the trouble shooting guide, it mentions this:
Problem: Red Indicator Light Is Flashing While Charging
A red flashing indicator light when charging indicates a selftest
error condition. Unplug the product and plug it in again.
Try this several times; if the indicator light continues to flash
red, unplug the GlowBuoy and take it to an authorized service