There are two parts to the "language of the shuffle light."
(1) Blinking means Do Not Disconnect. Not blinking (solid color) means OK to Disconnect. If it is blinking, you need to click the small Eject button next to the shuffle (in the iTunes sidebar) before physically disconnecting it from the computer.
(2) The Color indicates battery charge status. Green means full (or close to full) charge. Orange (yelow) means lower charge. Red means very low charge.
It blinks Orange, but it will never blink Green. So, even if the battery is fully changed, if the shuffle needs to be ejected before disconnecting, it will be blinking Orange. However, if you eject the shuffle without disconnecting it, and the battery is fully charged, the light should turn solid green.
This article has more details...
http://support.apple.com/kb/HT4310
NOTE: If you use automatic syncing by setting up the shuffle's Music tab in iTunes (instead of the Manually manage music setting), with disk use NOT enabled, iTunes automatically un-mounts the shuffle's "disk" when it is not being synced. Then, the light turns from solid Orange to solid Green when the battery is fully charged, and you can disconnect it without first ejecting.
