Got curious about this.
One notable difference between X11 and W3C is the case of "Gray" and its variants. In HTML, "Gray" is specifically reserved for the 128 triplet (50% gray) . However, in X11, "gray" was assigned to the 190 triplet (74.5%) , which is close to W3C "Silver" at 192 (75.3%) , and had "Light Gray" at 211 (83%) and "Dark Gray" at 169 (66%) counterparts. As a result, the combined CSS 3.0 color list that prevails on the web today produces "Dark Gray" as a significantly lighter tone than plain "Gray" , because "Dark Gray" was descended from X11 – for it did not exist in HTML nor CSS level 1[8] – while "Gray" was descended from HTML.
"Hey kid, hold still while we throw some fake money on you and take a photo. It's for marketing."