We don't have to. Nothing forces anybody to buy a car if they don't want one, whether it is black or not or new or not. The price of any commodity (including cars of all ages and colours) is decided by market forces.
You dont. Most manufacturers offer black along with red, blue, white etc.Metallic black costs more, but it is the same price as the other metallic colours.I am buying a new car next month, I visited many showrooms and that is how I know.
you pay more insurance for a black coloured car, but not sure about more when you buy it.
this is because a black car is harder to see and someone can crash into it. same with similar darker colours