My TV is screen is showing flashes of green light when watching a show, almost like a negative picture affect, is there something with the TV Ariel or the Sky box ? I can't determine, but i personally think its the Ariel.
I can't see how you're using an aerial (rather than a satellite dish) with a Sky box anyway!
The problem you've described can sometimes occur simply because a Scart or HDMI lead isn't plugged in properly. Try unplugging everything and then reconnecting.
However if the problem occurs BOTH when you're watching terrestrial TV (received via an aerial) AS WELL AS when your TV is taking its input from a Sky box, then the TV set itself must be faulty.