Muslin Grey (D4014) looks like gray marble: a pale ground, white and darker gray veining, and one speckled dark patch. It’s an Armstrong 16x16 vinyl tile from the Gravity design in the Alterna line, finished low gloss.
Armstrong lists the tile as waterproof, though the subfloor still has to be dry and flat. It’s a glue-down, set in full spread, and approved for any grade level. If you want grout, there are four recommended colors, Blue Ash and Mist among them, and the S-693 never gets sealed. A lifetime limited residential warranty and a 5-year limited light commercial warranty come with it.