PBT Cocktail Book, originally in The Mixicologist by CF Lawlor in 1895,  French for "jewel," some believe the colors of the three primary ingredients represent precious stones: diamonds, rubies, and emeralds.  

I'm Just Here for the Drinks by Sother Teague, page 37.  I misread the recipe to use Gin instead of Old Duff Genever.  Book suggestion:  Make it royal by substituting sparkling wine for the seltzer.

PDT Cocktail Book, pg 162.  I don't think it's supposed to be this color so assuming I didn't measure something correctly.