It’s really sad that you are going to have a job fail here, because your installer should be the one recommending the grout and charging you for the sample grouted panels. And if you can’t even talk to him, he probably isn’t qualified to do epoxy. Not that epoxy is ever needed in a home. It’s rubbish and causes way more problems than a homeowner thinks it solves.

Which colors are you using? grout line width? is the installer someone who's used to doing epoxy grouts?

Nice Skippack. Questions before lectures is always a wise move.

In my experience the grout kits are pretty close to the final product if the installer follows manufacturers instructions.

You have your tile person show you test s of the grout that is how you know for sure Yes Skipppack is right .

Why epoxy? It yellows over time, and does not solve any issues that you may have had in the past with mold. Better ventilation and waterproofing is what solves that.

I choose epoxy or urethane grout because it doesn;t stain and can easily be wiped clean. Mold isn't a consideration. Tilers need more skill, more time and good time management to use those products. They won't ever see your floor after they leave. Durability isn't always a high priority for all of them. Talk to several until you find a competent one.