The basic colour terms for black and white appear in (almost) all languages. Often, they are the only colour terms the particular language may contain (see the Universality and Evolution Theory), and in this case the refer to different shades of grey or presence (absence) of light and (therefore) they are called macrocolours (i.e. macroblack and macrowhite).
Czech and Finnish contain more basic colour terms than these two, however, in toponymy of these two language areas the prevailing colour terms are black and white, which at the same time behave (or are percieved) differently than colour terms used not as propria but as common nouns. Their semantic scope is much wider and more similar to the situation when there are only these two colour terms used in the language (i.e. more like macrocolours).
The wider (macrocolour) meaning is ascribed to these toponyms and it appears either in the motivation or in the later explanation which may or may not be correct (folk etymology).