I'm pretty sure my LED flashed "red" when the battery got low. It ran completely out due to USB port coming "off". I was too busy trying to delete accounts before sending off for RMA, before battery died, but again...pretty sure it was red.
If i understand right, /etc/mce/mce.ini has a section for defining led patterns for diferrent situations. For lovers of extreme sports, it should be possible to modify these patterns to your liking
Unfortunately, my brain is shutting down, so i'm rather not go into more details than give wrong advice