No. It is true that lighter colors reflect more sunlight, which means the shade itself will not absorb the heat of the sun as quickly. This, in turn, means the area directly around the shade does not suffer as much from the radiated heat coming from the shade. This is not so important for a shade sail that is well ventilated but when the same shade cloth is used as part of a roller blind or against a window it can make a difference. It is wrong, however, to assume that being under a darker shade will be hotter. Yes, the darker color will absorb more of the heat and light, rather than reflecting it, but the material is of such lightweight that it doesn't really retain the heat, whereas something dense and solid, such as a flagstone does retain the heat and stay hot, even if it is a light color. The shade sail's low thermal mass means that it cools easily just with the flow of air up through the mesh. Lighter colors also have a lower shade factor (it is brighter underneath them) compared to darker colors of the same material. When light hits a lighter color the higher reflection causes the surface to appear brighter, with more glare, often making a darker color more suitable.