A natural grey is what we used here. The original installations used the mortar grey when they did installations a 100 years ago.

Thank you for your help. Did you use the natural grey for the subway tile as well?

Yes I almost always recommend natural grey for all tile installations unless you have a very specific idea. It allows the tile colors not to compete with the grout.

I am assuming "natural" grey is a description and not an actual proper name for the grout color? Just wondering what the actual name and manufacturer is for the grout?

Natural Grey is a color choice for Custom Brand grouts. Any grey is acceptable it is when you use colored grouts it is not authentic to the period choices.

How do you maintain the grout colour? With time it gets darker on areas of more traffic, not even with a steam mop you can make it even.