What does it mean when the charger light is red instead of green

Actually when the light on the charger is Red it means not to unplug it because the battery is below 10%. The Orange is when it is still charging but not yet finished. Green is fully charged. Think of traffic lights and signs.

Red = No, Stop…………….. Don't unplug the charger
Orange = Caution………….. You can unplug the charger but watch the battery or I'll turn off on you.
Green = Yes, Go…………… Yes you can unplug the charger without worry.

I thought it looks more orange, but that means it has not finished charging yet.

Try an SMC reset:

Resetting the System Management Controller (SMC)

Resetting the SMC on Mac portables with a battery you can remove

1. Shut down the computer.
2. Disconnect the MagSafe power adapter from the computer, if it's connected.
3. Remove the battery (to remove the battery - click here: MacBook or MacBook Pro).
4. Press and hold the power button for 5 seconds.
5. Release the power button.
6. Reconnect the battery and MagSafe power adapter.
7. Press the power button to turn on the computer.

Resetting the SMC on portables with a battery you should not remove on your own:

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.

TThank you so much!!

my MacBook has been sitting dead in a cupboard for a year as everyone told me that it was knackered. I follow your advice and now it's working!!!!!!!

thank you again.... True genius

Ahh... no, but thanks for your enlightening interpretation of roadway traffic control devices.

The charger light is not like a traffic light. It only has two colors, Green and the other one (Call it red, orange, amber - take your pick).

Ciao.

I thought my color vision was failing. THANKS! You reply was very concise and informative. I didn't need to reset SMC though.

You got it right. Somebody should take points away from Oglethorpe for his false reply! 😀