Because the iPod Shuffle has no screen for displaying messages, it uses the status light's colour and blinking to give you messages. While charging, most of the blinking has to do with how much charge is currently available on the iPod Shuffle. Only one blinking light combination indicates an error.
Blinking Orange and Green
A blinking light that alternates between orange and green is an error message that means the iPod Shuffle needs to be restored. Plug it into your computer and open iTunes for further options.
A solid green light while charging means it's fully charged. When you first turn the iPod Shuffle on, blinking green means there's somewhere between 50 per cent and 100 per cent charge.
Blinking orange light means the iPod Shuffle is either syncing with iTunes or it's in disk-enabled mode. It might still be fully charged: check iTunes for the status.
A blinking red light indicates an extremely low battery --- less than 1 per cent. Leave your iPod Shuffle plugged in for a few hours if possible.