There has been criticism that the traffic light style of label is too simplistic. There are a number of competing styles of labels, or formats of labels, but none of them is perfect. I think we have to admit that. They all have strengths and weaknesses.
The strength of the traffic light format is that it gives people a very quick picture of the strict facts, but also an overall assessment. They can see at a glance, if they're concerned about fat or salt and it has a red light, that it's something they should stay away from. That format also usually gives objective information on the amount of each nutrient. Just having that amount alone doesn't seem to add much to what we already have.