Now, everybody seemed to be happy with your proposed solution except one dwarf. He stood and then asked, 'I have understood everything but why have you given '0' a different colour?' You were about to answer to his question when Shubhlin stopped you and told: I will answer your question sir. '0' is coloured differently because it is-
is neither positive nor negative integer
0 is coloured differently because 0 is neither positive nor negative integer.