The convention today is to use a powder color that provides a visual contrast to the surface being processed; dark surface = light powder, and light surface = dark powder. Rather than using black powder for everything, other colors (white, silver/grey/aluminum, or bi-chromatic) can be used to process almost any surface that may be encountered.
White powder works especially well on glass, chromed metals, plastic bags, and dark-colored surfaces. Aluminum powder performs best on glass, plastic, and rubber. Bi-chromatic powder, on the other hand, is typically a combination of black and aluminum powder, although some manufacturers combine the black with a variety of other colors. The idea behind the creation of the bi-chromatic powder was to assist the examiner with multi-colored surfaces. When processing with bi-chromatic powder, developed latent prints will be seen as black ridges on the light parts of the surface and light ridges on the dark parts of the surface. Once these prints are lifted, they will always visualize as dark ridges on a white backing card.