My tablet turns different colors when I turn it on

When I turn my tablet on it will change colors whitch is green red yellow ,when I tap or turn it at different angles it will sometimes be alright ,if i press on the back it will be alright but it won't stay that . this is the 3rd on I have had in a year and a half the 1st lasted 3weeks the 2nd on about 6months this one l have had less than a year ,can I be fixed? Thank You Donald Dennis