Why does the rainbow have 7 colors?

Why does the rainbow have 7 colors?

Because Isaac Newton thought that 7 was a number with special meaning and divided the continuous spectrum into 7 discrete colors. Newton believed that the number 7 was part of a universal harmony, having 7 musical notes, 7 planets (those known in his time), etc... so it seemed to him that he should divide the rainbow into 7 colors to continue with that harmony .