For my bathroom, I want it to look very modern and sophisticated. I really like the distinction between black and white, as opposing colours, and in an odd way, a very light blue to black or white to a very dark purple also match quite well in this room.
For my colour palette, I looked at the gradient of white to black (1), light blue to black (2) and off white to dark purple (3). After looking at these images I decided to go with the white to dark purple. However, for shadows and darker areas, I would go for a darker purple and try to avoid black as the bathroom is a generally well lit area of the house.