In other words, they probably bear a distant relation to the semiotics of the stoplight, and that's probably why red was chosen for ambulances and police cars: because they put into your head the notion of "stop."

这很可能是源自于,红灯在一些语义中表示停止的意思，它被应用在了救护车和警车上：,因为他们带有警告的意味“

耶鲁公开课 - 文学理论导论课程节选

You can still in France today find not canine butchers, you can find horse butchers, and it's always a red front with a gold head of a horse, appropriately enough.

现在,在法国,你仍然可以看到杀马的屠户,通常都是红色门面上贴着个金色的马头,十分相称

耶鲁公开课 - 1871年后的法国课程节选

Inside the head it's bright red because it's pulsing with blood.

在颅内的时候,它是鲜红色的,因为它充满了鲜血

耶鲁公开课 - 心理学导论课程节选