USGS topographic maps use the following colors and symbols to designate different features
Black - man-made features such as roads, buildings, etc.
Blue - water, lakes, rivers, streams, etc.
Brown - contour lines
Green - areas with substantial vegetation (could be forest, scrub, etc.)
White - areas with little or no vegetation; white is also used to depict permanent snowfields and glaciers
Red - major highways; boundaries of public land areas
Purple - features added to the map since the original survey. These features are based on aerial photographs but have not been checked on land.