As glad posted, we used gray grout, but I'm not sure what kind or what color. The tile guy just presented me with the choices and I picked one. I didn't write down what it was. I used flat white subway tiles in the upstairs bedrooms and the first tile guy I had grouted it white (after I had repeatedly told our builder I wanted gray grout). To me, it looked terrible. To me, the pattern is the point of the subway tile and if you don't use a contrasting grout the pattern is lost. Needlesstosay, the tile guy had to dig out all the white grout and start over. We had a new and much better tile guy by the time we got to the kitchen and the laundry.

Can't picture it, but try Houzz Here's what came up by searching on Herringbone+pot filler+corbels. https://www.houzz.com/products/products-pcat-br~-%2B-pot-filler%2B-corbels

I have the Subway Ceramics Avalon / Minas with a medium gray grout. And a Shaw's white sink, if anyone is considering that, by the way. (My contractor could have ordered it directly, but at his request, I went through a tile store, and by the time everyone had put their sugar onto it, it was OBSCENELY expensive.) I'm not an installation expert, but at least with the Subway Ceramics, the installers use little plastic spacers between the tiles (I think some others have their own spacers?) when they put them up, they don't do it freehand, so how much grout you get is a function of 1) the limits set by the curvature of the tile and 2) what size spacers they use. So you might be willing to go a little darker with a smaller grout line, or with a handmade tile that refuses to go close together, you might want to stay light. The traditional color is close to concrete. But most modern people don't seem to like that, so do what pleases you!

While not labelled as such, im thinking the Subway Ceramic images are prob that narrow. Here is a link that might be useful: subway grout