Whilst there are some foods which seem to be black, most are found to be very dark shades of other colours on closer inspection. This includes currants, and blackberries for example which are both dark shades of red.
Natural black colour is desirable however in the case of foods which require a burnt taste or look, such as ready-made pizzas, when biscuits or chocolate need to be darkened to an almost black colour, or in the manufacture of black sweets such as liquorice.
The source of natural black colour is always the same, it is made from the carbonisation of vegetable matter at high temperature. The resulting colour is highly light, heat and acid stable. Milling of the material results in a very fine powder, which can then be suspended in a liquid to make the colour easier to handle and disperse in the application.