Modern color is when color has been added to a map or print well after its initial release. This usually happens by a collector / reseller who wishes to increase the appeal, and therefore resale value, of a map or print leaf. This is contrasted with contemporary color where the map or print was colored as part of the original publishing effort.

Individual leafs from older books tended to be uncolored. Most maps and prints of this type had very basic, if any, coloring. Many books, atlases, and prints in the latter half of the 19th century began to incorporate more color as printing techniques changed. As the printing became more available to the public (mass produced) the quality changed for the worse. So as contemporary color increased, the modern appeal tends to decrease.

The result is a strong appeal for older maps with a period feel that have color. This is frequently provided by modern means. Most types of collecting will not tolerate modern modifications to a historical item, but map collecting (unfortunately - in my opinion) seems to have little problem with these modifications.

One important downside of map coloring is the imposition of concepts that the engraver was not intent upon expressing. For example, what color should one use for "Felix (Fertile) Arabia"? How about the color used for the internal parts of Africa? Was the engraver following Ptolemy, medieval thought, or actual reports of travelers? Only the engraver can say, and adding color to maps like this is effectively changing the engravers / map makers expression of the world.