I'm currently building a 250 sq ft flagstone patio in Austin, Texas. I'm wondering what work best for grout between the rocks. I've heard of folks using polymer sand, dg, or mortar. I don't like dg for this because I prototyped it on a small area and it tracked in too much into the house. Also wondering about color additives if I go the mortar route. I think this final finishing is absolutely key to making the project a success so I don't want to mess it up!