Tiffany Blue is the colloquial name for the light medium robin egg blue color associated with Tiffany & Co., the New York City jewelry company, created by Charles Tiffany and John Young in 1837. The color was used on the cover of Tiffany's Blue Book , first published in 1845.  Since then, Tiffany & Co. has used the color extensively on promotional materials like boxes and bags.
The color is produced as a private custom color by Pantone, with PMS number 1837, the number deriving from the year of Tiffany's foundation. As a trademarked color, it is not publicly available and is therefore not printed in the Pantone Matching System swatch books.