Paul, i agree. Color plates would have been amazing (and probably expensive, too). On one of the first pages, it says that:
These copyrighted designs are reproduced by kind permission of "The Artistic Supply Co.,"Amberley House, W.C. The posters, with very few exceptions, are from photographs specially taken by Mr. James Hyatt.
What I also find fascinating, is the last chapter, which deals with poster rarity and value. Even at the end of the 19th century, posters by artists, such as Cheret, were highly collectible, and tidy sums were paid for his works. Some of the most valued, back then, had prices of 100 francs or more.
So it seems that poster collecting has been a vibrant hobby for quite some time.
Jeff