Are you certain it's the TV and not from the source (cable or satellite feed)? Once you're certain, either return it to the place of purchase if you're within the allowed time or contact the manufacturer for a replacement. It sounds like a defective video processing chip or a partial short in a circuit board. Get it fixed or replaced while it's under warranty.
Be aware, most replacements are refurbs and you then lose your original warranty, getting a 30, 60, or 90 day warranty on the refurb or repair. If it has a problem again, contact them IMMEDIATELY. Also, check your state's attorney general website (consumer protection division) or call them and check on your state's lemon laws. They usually only apply to cars, but some states also cover appliances and/or electronics. It's generally 3 repairs or problems within 6 months or a year, and the mfr. will be required to provide a brand new replacement at no charge (no shipping charges, etc).