TheyA black box (generally speaking) is a device or box whose internal working are not of as much interest or value but rather the input and output.
Flight data recorders are orange so that they can be located easily in case of a crash. If they were black, they can be camouflaged by their surroundings.
Bright orange color make them stand out easily, because nature didn't make many things orange, besides oranges.
Another reason is that they are painted/coated with heat-resistant bright orange paint.
By the way, their actual or correct name is "flight data recorder".
Update
A black box (generally speaking) is a device or box whose internal working are not of as much interest or value but rather the input and output.
