What does black and white make

Usually a grey color, dark grey or light grey. It depends on how much black and how much white is mixed just like paint.

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.