rgb.txt
X11's list of colour names, AliceBlue, PapayaWhip, DarkSlateGray and the rest, which by way of Netscape and SVG became the colour names CSS uses to this day.
The file rgb.txt, originally in /usr/lib/X11, maps around 750 names to RGB values so a program can ask for -bg NavajoWhite instead of a hex code. The basis dates from the mid-1980s, but in 1989 Paul Raveling at USC/ISI recalibrated the values against his own HP monitor, and the following year John C. Thomas added an entire paint-shop colour chart, which is why so many names sound like desserts. There are also gray0 through gray100, in both American and British spelling, so nobody would have to do arithmetic.
Netscape Navigator accepted the X11 names in HTML, SVG 1.0 wrote them into a standard in 2001, and CSS Color Module Level 3 made 147 of them official. The seam shows: HTML's original sixteen colours came from the VGA palette, so in CSS gray is darker than darkgray, and green is #008000 while X11's green, #00FF00, had to be renamed lime. The showrgb command prints the file, and copies of its values turn up in Tk, Emacs and most things that have ever needed to know what "chartreuse" is.