Getting ready to tile shower. We decided 4x12 white subway tile for wall and 2 x2 white hexagon for floor. My wife wanted to go with a charcoal/ black grout, which I thought would add a nice retro look. Problem is I've read to deep into all the different types of grout and now have no idea which way to go. At one point I was going epoxy, then it was acrylic, then it was urethane. I know they all have pros and cons. Costs aside, I want what's going to work for our situation. We are in the south along FL panhandle. Water comes from well. We can have things from iron, manganese and coliform in the water. So we obviously want a grout that is going to withstand the toughest water stains and mildew. We want strong and long lasting. We would prefer to retain color as long as possible. What are your recommendations?