An international treaty requires the "go" light to be green, so why does Japan often substitute blue? The answer has ancient roots in the nation's language.

Before we’re old enough to even see over the dashboard, we learn that green means go and red means stop. This internationally recognized traffic light color system is standard in most of the world.

You might have seen traffic lights in Japan that are a little different to what you're used to. Instead of being red, amber, and green, the last light on the signal might be blue, or perhaps an ...