The X11 color palette used here is a collection of 140 colors developed by the Massachusetts Institute of Technology (MIT) for the X Window System. It was first published in 1987 and has since then become an important standard for representing colors on computers. The palette includes a wide range of colors, including primary colors, pastels, shades, and blends. The X11 color palette is still widely used today, especially in web development, to ensure consistent color.