With the exception of some early 16th. century maps on which the place names were printed in red all early maps were printed in black and white. However, it was not long before map publishers discovered that colouring maps made them more attractive to the buyer.
Watercolour was the medium used and colouring large numbers of maps by hand was a slow process so maps were offered as coloured or 'plain'.
By the 17th.century map colouring had become a trade in its own right and the highly decorative maps of the period with their elaborate cartouches gave the colourist plenty of scope to exercise his imagination. Certain parts of a map however were subject to a common formula : parks and woodland were coloured green ; seas and rivers, blue ; hillls, brown and towns and cities, red. When it came to armorials (coats of arms) a strict heraldic code had to be adhered to : as a guide to the colourist the direction of the engraved lines on a shield indicated which colour should be used eg. horizontal lines meant blue, vertical lines meant red should be applied.
In contrast to the highly decorative and richly coloured maps sometimes only the boundaries between districts or counties were coloured, this is referred to as outline colouring and is more commonly found on later, plainer maps.
Original or contemporary colouring means colouring that was done when the map was printed.
Later colouring means colouring that was applied some time after the map was printed.
Today it is normal practice for dealers in antique maps to have them coloured if it is thought to be appropriate and recent colouring does not diminish the value of a map providing it has been well done and carried out in sympathy with the map's period. Well executed recent colouring is often hard to distinguish from original colour