If it were me I'd use a light gray. Custom Building Products sold at home depot, colors #115 Platinum, 544 Rolling Fog or 546 Cape Gray would look nice.

Three years ago we put in a similar basket weave, but with black dots. It is in our ensuite, but it has not been babied in any way. I wish I had used a darker grout than I did. With the light grout you really see the build up of dirt in the grout lines. I think that the build up is inevitable in a marble floor with tiles that small, but I think that going with a darker grey grout would have camouflaged it more. Attached is a photo I just took of the area where I think it is most obvious - around the toilet. You can see the area where we never step (at the top of the photo), compared to the area of the room that probably has some of the heaviest foot traffic (at the front).

I'd go with a light gray... however, I would try to visit a tile store to get an idea by their grout bars vs. picking off of the label of a box and color at a big box store. Then you know better what you lean toward. If you have, "The Tile Store" in your area, they have different types of grout bar samples you can see them with the tile.

Hi! Curious what color you went with? I’m using tile that looks identical in a high traffic powder room and trying to make the same decision.