為什麼警燈是紅藍兩種顏色？

好像世界上的警燈都是這個樣子吧？連消防、救護車都是這個樣子，這有什麼來歷么？

網上查了一下，有很多種說法：

1. Blue is easiest to pick out during the night and red easier during daylight. 藍燈在夜間更顯眼，紅燈在白天更顯眼 Next time you see a police vehicle"s lights on, stop and think which one pops more depending on the time of day. 下次你遇到紅藍警車燈的時候你可以觀察一下~~

2. Until the late-50s, all of the police lights were red. In the late-50s, OW Wilson became the chief of police in Chicago and, to distinguish between the police and the fire, he had the police lights changed to blue. Other departments, confused to be sure, changed to both blue and red. 在美國50年代以前，所有的燈都是紅的，後來某位同學在芝加哥上台之後，把Police與Fire分開，於是Police就變成了藍的，在後來，其他部門都很鬱悶很彷徨，就索性兩種都用。。。

3. Red: Warning 傳統意義上的警告色, Blue: Emergency 緊急事務

4. 不知道你能不能打開這個鏈接：Why Do Police Cars Use Red Blue Lights? They"re Visually Confusing 大意是說，紅藍閃光會讓人眼難以定焦，以造成心理上的不適，來達到警示的效果

比如這樣：是不是覺得識別上面的文字很困難，眼部會非常不適。。。快瘋了。。。

4. 還有。。。等會更新