I know that western cultures used to view ghosts and spirits as dark or black (hence the term "shade" and the pejorative "spook" for black people), while modern American culture and West African traditions have ghosts being white (there was even at least one unfortunate incident in which an isolated group mistook European explorers for ancestral spirits). Was the switch in American culture a cultural import from West Africa via the slave trade?
Nope. The depiction of ghosts as white specters or phantoms has a long tradition in Western Europe, dating back to (at least) the medieval period. While medieval texts are usually not very descriptive with regards to the color of the dead, there are a couple of examples I can think of dead clad in white, but perhaps more useful are several illustrations that depict the dead cloaked in white shrouds, or semi-translucent. For example:
While it may not be as apparent in the second image, in the color copies I have in my books, the ghost from the Cantigas sort of blends in with the background. Depictions of ghosts in this manner (white or translucent), however, were not the only way of depicting the dead, in prose or illustration, nor was it even the most popular. Macabre depictions of the dead as corpses were certainly more widespread beginning in the 15th century. The standards for what constituted a 'ghost' --a bit of an anachronism-- encompassed a diverse set of possible descriptors and elements. The dead returned to meet the living in a variety of different forms, colors, shapes, etc.
Now from what I understand, and it's a bit outside my area, the image of the white phantom experienced a surge in popularity in the nineteenth century. As far as I am aware, it did not have anything to do with West African traditions, but perhaps someone better versed in that time period can contribute.
