X11.

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 – while "Gray" was descended from HTML. Even in the current draft for CSS 4.0, dark gray continues to be a lighter shade than gray. Some browsers such as Netscape Navigator insisted on an "a" in any "Gray" except for "Light Grey".