The pursuit of historically important maps has been a passion of mine for 45 years.
By far the best part of the experience has been learning the essence of history through maps. While they certainly don't tell anywhere near the whole story they DO provide a visual guide to the results of exploration, political boundaries, the obstacles and advantages of geographical position for trade and the progress of art history through design motifs.
Another advantage of map collecting is that the corpus of reference books is extensive. Using authors such as William Patterson Cumming, Seymour Schwartz, R. V. Tooley, Nebenzahl, Tony Campbell, Henry Stevens, Martin and Martin one can quickly come to the realization of what truly is important and worth owning as opposed to what is derivative or even wrong when better information was available.
Of course, owning maps that are exactly as they were plus normal oxidation is key to the full enjoyment of possession.
The history of map coloring in the 20th century probably had it greatest impetus because of American tourists in London in the 1960's. Maps then were relatively inexpensive and easy to obtain. With virtually no sophistication it is easy to understand why the London trade would find upper middle class professionals from the East Coast and the Midwest easy prey. In fact it is my opinion that R. V. Tooley, Roger Baynton-Williams, Jonathan Potter, Weiss and quite a few others just didnt see anything wrong with the practice until I started saying it was wrong in the 1980's.
Then the fraud started to creep in as my proselytizing against new color took hold. My broadcasting that a sheet of paper from the 16th century with color applied in the 20th century was an obscenity drove the practice underground.
Still it was then easy to tell the difference because there was no oxidation of the copper in the green pigment on the back of the map. A simple flipping of the sheet was all that was necessary to tell the difference.
Of course the news of this spread to all collectors and it is now when the fraud started to occur as a conscious attempt was made to start faking original color.