Question

why the roads are of only black coloured

Answer 1

beacause of its ingredients

Answer 2

All roads are not black in color. Roads which made of asphalt are black in color. Concrete roads can be almost white in color. Asphalt is like liquid tar and is black in color. It is what holds the rest of the components in asphalt paving together, thus coating all of the components with liquid asphalt and making them black.