Two colors with one name
Ask for maroon in a web page and you get #800000, a dark brown red. The code on this page, #B03060, is the maroon of the X11 color list instead. X11 is the window system used on Linux and other Unix computers, and it came with its own list of color names.
The first web browsers, Mosaic and Netscape Navigator, were X11 programs and borrowed that list. When the web's standards group wrote the official color keywords, it kept maroon as #800000 from the 16 basic colors of HTML 3.2. That left the word with two meanings, as the article on X11 color names explains.
Since 2014, X11 accepts both. X11 Maroon means #B03060, and Web Maroon means #800000. Wikipedia calls the X11 shade rich maroon, and this site also lists the same code as rich maroon. The web version is maroon (HTML/CSS).
Four numbered maroons
Like many X11 names, maroon comes in numbered versions. Maroon1 is a hot pink, #FF34B3. Maroon2 and maroon3 get darker step by step, and maroon4 is a deep plum, #8B1C62. None of them look much like the brownish maroon most people picture.
Named after a nut
The word comes from the French marron, a chestnut. English speakers began using maroon for a color in 1789, according to Maerz and Paul's A Dictionary of Color of 1930. White text on the X11 shade reaches a contrast ratio of 6.11 to 1.

