Hello Bbabers,
I've posted this elsewhere, but I don't mind repeating it. For very tight-set tiles, I like to use mason's string in long lengths laid into the horizontal joint as a spacer. The string is then carefully pulled out, like a rip chord, before the thinset has gotten hard. This method allows me to lay flat edges on the face of the tile, to assure that everything is "in plane" and to wash things up without disrupting the spacers.
I've liked some of the very faint gray grouts (non-sanded of course) but there are too many variables to suggest a specific color now. Investigate which grout manufacturers are available to you and then get sample chits for the colors you are considering. I carry color boxes for five grout manufacturers and will often pull them all out when I am working with a client on color choices. I've got my preferred brands, but they each have unique color palettes so I show them all.
More important than brand is the expiration date of the grout and whether the supplier adequately rotates their inventory. When you find the color you want, confirm with the supplier that the dates stamped on the package indicate a "fresh" grout. Cementitious products aren't generally reliable past 1 year after manufacture.
Best of luck,
Shaughnn

Thanks so much for this detailed explanation. I'm thinking the color I picked is a little bit too dark gray even thought it is the lightest one of three different brands of grout I was shown. Am I understanding that the spacing is about 1/16th or is that even less? Again, thanks for your help.

Hi again Bbabers,
Which colors are you considering? Are you only looking at the gray tones or are you also considering some of the whites too? With the mason's string, you're looking at around 1/32" or less (depends on the string used)
Shaughnn

I'm good with white if you think it would better give the look I want. I just don't want it to look dirty or too off white. Would you mind suggesting some whites you think would look good? My installer has offered me color palettes from TexRite, Polyblend, and Mapei.

I'm not a fan of Custom Building Products grouts but I do think they have one of the better selections of colors. I've liked Custom's "Platinum" with white field tile and tight joints. It's a pretty faint gray. I'd also consider "Snow White" as it's got some blue in it. Can your installer get sample boxes for either Laticrete or Hydroment?
Shaughnn