Question

black is a color, white is also a color but why black and white television is not a color television

Answer 1

because all other colours cannot be seen in their originality, black denotes only that some part has colour but that colour cannot be seen, white denotes no colour or lighter colour in that object.hence black and white just make us experience the difference between things which makes us know a scene.
suppose u are playing a shadow game then the shadow appears black remaining part appears white but we can't say that we are seeing a scene with colours