A red light symbolizes caution. You see a red light in traffic, and you stop, not necessarily for your safety but for the safety of others, oncoming vehicles and pedestrians.
In another instance, a red light in 17th century Amsterdam allegedly both camouflaged patched skin and signaled the availability of a sex worker to offer pleasure. Here, a red light symbolized an invitation.
Very often, as with other concepts like money, etiquette, specific words and so on, it’s not the concept about which, we should concern ourselves but the social conventions that surround these concepts.