A reset or re-calibration of your Phantom’s IMU Compass will need to be completed if you are still receiving yellow and red flashing lights after using the normal compass calibration process.
The problem occurs because the drone’s compass has come close to a strong magnetic field. This problem only happens in GPS mode and not in altitude mode.
Follow the instructions in this article and or scroll straight down and watch the video which shows you how to re-calibrate the compass on your Phantom 2.
If you own an new Phantom, read and follow these instructions for the Phantom 3 IMU calibration and Phantom 4 calibration procedures.
Another great article with video is on how to improve the gps signal on your Phantom 2.
The Phantom 2 is a terrific quadcopter. The best and most beautiful drone videos on YouTube have been filmed using the Phantom and GoPro Hero combination. I hope this article and video instruction gets your compass calibrated again so you can get back out doing what you love best. Flying your Phantom.