I think it's supposed to be simulating dripping paint, but on this Eve of the Apocalypse, I wouldn't be surprised if Animi Causa's powder coated metal napkin holder actually started dripping blood. That's definitely what it looks to be doing anyway. I'm sure that was the intended effect too. They could have loaded the blue napkin version as the featured image. In fact, I might have to click over to that one for a while. Until the sense of impending doom sloshing around in my gut subsides.
Dripping napkin holders invite the insertion of any color napkin your heart desires, and if your heart desires anything other than disturbing guests and fellow diners, I'd recommend one besides red. And maybe green as that would look like the remains of a poor Ghostbusters slimer. The holder measures 6.7" x 5.9" x 2". I presume it holds napkins slightly smaller than that.