Brought to you by the unholy marriage between incompatible, pre-existing standards.
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.
