Why are the colors weird on my Wii U gamepad?

There are a few simple tweaks you can make to resolve the inverted colors. First, try rebooting your Wii U. If that does not work, check your system for any updates you need to perform or if the HDMI port is damaged. This troubleshooting guide outlines all the possible solutions for this problem: Nintendo Wii U Troubleshooting

This might be caused by a game. If not, try getting a new HDMI cable. If that won't help, your port on your TV is broken, or the port on your Wii U. If you tryed a different TV and it was still inverted, you need to give your Wii U to Nintendo Technical Support.