Why my MacBook Pro 15" (2011) power adapter turns orange?
It could be that your battery is defective.

If you go to System Information &gt; Power, what do you see under "Battery Information" - "Charge Information"?

Mine says:

Charge Information:
  Charge Remaining (mAh): 4693
  Fully Charged: Yes
  Charging: No
  Full Charge Capacity (mAh): 4744
Health Information:
  Cycle Count: 219
  Condition: Normal