Maps were initially colored for aesthetic reasons and to improve readability. The most commonly used colors were green, pink, orange, and yellow for political subdivisions; red for cities and towns; green for forests; brown for mountains; and blue for seas.
Color on maps may have been applied shortly after the first printing (original color) or at any subsequent time.
If not otherwise stated: Colors have been applied by hand.

We use the following color keys in our catalog:

Original colors mean the colors were applied around the time the map was issued.

Original o/l colors: means the map has only the borders colored at the time of publication.

Colored: If the colors are applied recently or at the end of the 20th century, then "colored" or "attractive colors" will be used.
If a cartouche was traditionally left uncolored (for example, in Homann's or Seutter maps), and recent coloring is applied, that will be mentioned.

Later colors:If the colors are applied somewhat between the date of publication and the end of the 20th century.

Later color application to a map originally printed in black and white does not make it a fake. Skillfully applied modern color enhances the beauty and thus, the value of many maps.
Old colors may have soaked into the paper and caused oxidation, especially green, whereas modern colors generally do not. The exact date of coloring is often difficult to determine with certainty.