Traffic light system for labeling food

There is a lot of talk about a traffic light system for food labeling so that people who don't understand nutrition can be told that what they thought was healthy is in fact like eating sweets for breakfast. Some food companies and supermarkets have taken the initiative and made up their own traffic lights. Governments tend to like this sort of thing. It takes responsibility from them and reduces the cost of 'regulating' a sector. More importantly perhaps it prevents them having to take on their financial supporters in industry. What politician would want to piss off a big multinational food company for example?
So in the absence of real certified traffic lights whose function is to protect citizens we get watered down corporate ones whose function is to prevent the introduction of the real thing.
Food companies in their search for marketing perfection scour their products to find good stuff that they can promote. This allows them to say that sugary cereals don't have any fat. If you eat them, you will have fat, but that is not the food company's fault. So the reasoning goes. I reckon when we do finally get traffic lights a red light in any of the monitored areas (fat, sugar, salt etc.) should result in a ban on any positive spin marketing claims for the product. Certain products are going to contain bad things, but if we are told this with traffic lights fair enough. A less savvy consumer though may not even turn to the side of the box if is is screaming 'fat free' at them.