Broadly speaking, small cars and dark colours are two things that generally dont go well hand in hand... one of the main reasons such daily runabouts are invariably offered in bright colours (PakSuzuki excepted), because they look attractive in those colours and appeal to the demographic that they intend to target - young buyers, mainly females..
That said, black colour, in my opinion, only suits luxury limos (BMWs, Mercs, Audis etc.).. a small car, that too something of the size/proportions/quality of Mehran, would most certainly look like a tar ball, than anything else, if offered in black..
Besides that, the already noted reason of A/C performance could also have a certain bearing on their decision not to offer it in black form.. but then again, I doubt that too, because I dont believe they might have put that much of a thought into such a scientific subtlety, after all we're talking about PAK-SUZUKI here..!! :-#
I thought it was darkness that was in fact the absence of light..
Technically, black indeed is not a colour (likewise white too), but not because of the absence of colour, but because it absorbs all the colours in the light spectrum and emits none.. conversely, white emits all of them, while for instance a blue emits only blue out of the 7 colours found in the spectrum of light...