Usually, when I plug my nookcolor to the charger, I see a orange/yellow n on the connector until it becomes fully charge and the n has a green light.
Today for the first time the n is a red light. What does that mean? It looks like the nookcolor is still being charged since I see the the battery % continues to go up. Does it mean that the cable is faulty or my nookcolor is not being charged correctly?
There was quite a discussion on this a while back (search "red light") and never really reached a consensus.
The most common answer was that it meant there wasn't a good connection between the nook and the charging cord.
Double check that your charger is firmly in the wall, the cord is firmly plugged into the charger, and then plug it into the nook again.
If it is still red, try moving the end plugged into the nook a little and see if the color changes. You could have a faulty cord, plug, or connector on the nook. If it doesn't straighten up. Take your nook and the cord and charger into a B&N and let them check it out. They can test your nook with their cord, and test your charger on their store unit.
My tablet is doing the same thing now too. it usually would blink back and forth between red, orange, and green but still charge (a little) since i got it.... however now its not charging at all. Off the the B&N store i guess!