X is for Xanadu, the color not the movie

So, there is exactly one color that starts with an X. Xanadu, the color is named after Xanadu, the philodendron plant, which in turn is named after Xanadu, the city (not Xanadu, the movie). Following so far? Good.
Xanadu was Kublai Khan's first capital, founded in the 13th century, and we all know it from Samuel Taylor Colridge's poem. And that is pretty much all I am going to tell you about it