White is virtually the color of most school uniforms. But it is usually limited to the blouse or shirt because the lower part of the ensemble (i.e. pants and skirts) gets dirty easily so they usually come in different colors and materials. Men would have khaki or black pants while girls would wear skirts of different colors and patterns and that is also how they are identified as to what school they are attending.
But as for nurses, nursing uniforms always come in white. And so are lab coats. It is really quite impractical because whites usually get soiled easily, even from your own sweat and from the grime of the day. And after several washes, they get stained from the impurities in the water. It is really labor intensive to keep washing them and soaking them in bleach just so they would remain gleaming white. So you will not wonder the next time you encounter a nurse with a bad mood. Chances are, they had difficulty washing off the stains on their uniform so they were late for work.
Well, at least now, people have choices for their uniforms at http://www.blueskyscrubs.com/. There are many different colors and designs to suit everyone's fancy. And they are affordable, too.