Change to a channel that isn't showing pics of the sky.
Umm.. seriously, none of us can troubleshoot your TV on-line for you and you haven't listed a whole lot of info for anyone to work with here.
It's possible that you've lost the red or green gun in the TV and it could be replaced if that is the case but you really need to contact a local service rep to find out what that would cost and then decide if it's worth fixing or not. Call around and see what local shops charge for repair estimates in your area.