Stub As with earlier posters, my first thought was to have the towel in your lap match as closely as possible what you're wearing, at least color- and pattern-wise.
I looked a bit for nice black tea towels, but they don't seem to exist! Also, black doesn't work well in our household because we have a white cat, and aside from the fur issue I can see cotton looking ratty and like a rag. I do have a black "performance dress" that gets sticky rolled right before I leave home.
I do think the towels I own are pretty and am thinking I should just own it! If I have one in my lap there really isn't any way to truly hide it.