Black Backed Solar Panels
Many people are now offering completely black panels, not only with black frames, but also with a black backing behind the cells instead of the traditional white. It is true that these do give a much better appearance, particularly on slate roofs or old traditional cottages with dark coloured plain tiles.
However, the problem with having a black backing, is that black absorbs light and heat from the sun. this means that you do not get the extra benefit of some of the sunlight being reflected back onto the cells by the backing material. Also, the panels get hotter. Solar cells, like most electrical equipment, are more efficient when they are cooler, so that panels with black backs are always going to perform less effectively than ones with standard white backing.
If you are concerned about the appearance on your property, then we would recommend having a halfway house of using a panel with black anodized outer frame, instead of standard aluminum, but still have a white backing material. REC, as an example, have told us that they are not even going to produce a black backed module, because their main concern is always to try to improve the electricity that their PV panels generate and black backing is a retrograde step.