What is the color of the black box in a commercial airplane?

Although they are called 'black boxes,' aviation recorders are actually painted bright orange. This distinct color, along with the strips of reflective tape attached to the recorders' exteriors, help investigators locate the black boxes following an accident. These are especially helpful when a plane lands in the water.

https://science.howstuffworks.com/transport/flight/modern/black-box.htm

In engineering, a black box is something which data goes into or out of, but we don't know or care what happens inside. The black boxes in planes probably got their name from this, although they are orange to make them easy to find after a crash.

http://news.bbc.co.uk/1/hi/sci/tech/2640793.stm

The "black box" on airplanes was invented by Dr. David Warren around 1954. It is first made with the a box being black but ALWAYS painted usually with the color "international orange".

http://inventors.about.com/library/inventors/blblackbox.htm

Black boxes, which are technically called flight data recorders and are not black at all, but a regulation shade of orange, with reflective yellow stripes.

http://query.nytimes.com/gst/fullpage.html?res=9B02E2D91131F933A15752C1A962958260

Who Invented the Black Box?

The Black Box was first invented by a young Australian scientist named Dr. David Warren. While Warren was working at the Aeronautical Research Laboratory in Melbourne in the mid-1950s he was involved in the accident investigation surrounding the mysterious crash of the world’s first jet-powered commercial aircraft, the Comet. Realising that it would have been useful for investigators if there had been a recording of what had happened on the plane just before the crash, he got to work on a basic flight data recorder. The first demonstration unit was produced in 1957, but it was not until 1960, after an unexplained plane crash in Queensland, that Australia became the first country in the world to make the Black Box mandatory for all commercial aircraft.

https://en.wikipedia.org/wiki/David_Warren_(inventor)

Still unclear why those orange painted box is called "Black Box". The Times of India offers an explanation:

The term "black box" was a World War II British phrase, originating with the development of radio, radar, and electronic navigational aids in British and Allied combat aircraft. These often-secret electronic devices were literally encased in non-reflective black boxes or housings, hence the name "black box".

https://timesofindia.indiatimes.com/india/airplane-black-box-all-you-need-to-know-about-the-device/articleshow/77434032.cms