Chez Chesler

The faucets in the bathroom in the building to which my employer's offices have just been moved are marked with red spots for hot and blue spots for cold. One either likes or dislikes (or doesn't notice) the introduction of hues in the otherwise monochrome bathroom. Are the spots language-neutral, in case some visitor to the bathroom doesn't know that C mean "cold" and not "chaud" or "caliente"? Who is this hypothetical visitor that doesn't realize that he's in America and who doesn't read any English? Why do the plumbing architects assume that this visitor, who also doesn't understand the convention that left means hot and right means cold, will understand that red means hot and blue means cold?