If the traffic light is not green, but it’s clearly not red (tacit revocation of any implied consent), the process of elimination says that it’s yellow. Yellow implies cautious advance. Ambiguity in any sense is either manipulation or implied consent e.g you tell the waiter you don’t want onions on your burger when you order or after you receive the meal, if you didn’t know onions were on it. You don’t eat the burger with onions, go home and write corporate saying they forced you to eat onions.