The game begins with no units on the board in Winter Adjustment, so powers decide which unit they would like to start with (if they are on a coastal supply center). Note that Spain and St. Petersburg require a coast specification for building fleets.
The colors are fixed as listed. There is no coloring scheme that will guarentee that two similarly colored powers won't share battle lines (and thereby make it difficult to read the map). The colors do not change later in the game to make it easier to read the map because that would be more confusing over all. The "border" maps tend to preserve the true colors better than the "texture" maps (due to the color limitations of the gif image format) and the "classic" maps have the abbreviations for the powers on the units.
Take care when viewing the maps.