I went to both the Bostik and Mapei sites and looks like you can get samples of grout (those small channels of grout you see in stores) for free from both of them. Suggest you get actual samples and compare. Or, contact Mapei through their website and ask if they can advise.

Thank you! I don’t have time to go to the store so I doubt I would get the samples in time but calling them is a great idea!

I’m in a similar boat—what color did you end up going with?

Maybe oyster gray by Polyblend at home depot?