If you tablet can connect to TV via a HDMI adapter, use it to verify the source of problem. You did not give a specific model so I have no idea which one your have. A rule of thumb, if anything is fine on TV but not on your tablet, the problem is from LCD. If both look the same, the problem is from main board.
Most of distorted images or discoloration problem just simply comes from a loose LCD cable. Reconnect and secure the connection with tape will solve the problem and prevent it from happening again, otherwise you have a bad LCD.
This is one sample of loose LCD cable, I did on purpose
