Hi and LOVE the BLING! I also worry about your tile setters skill set. If they are not top notch you could have some problems.
You play with the different color of thin set by getting some paint sample cards in off white, lightest gray, a bit darker gray. Put the tile on top of each one outside where the pool is going and see what you think of each one. I would ask the tile setters if they have done tile like this before. If they say yes ask them to show you the first set of tile done. IF they do a good job let them keep going BUT bring them goodies every once in a while AKA check on their progress and skills in the name of yummies.
Now think about what color of grout you want to use. White will allow the tiles to blend together. A light gray will allow them to pop out a bit. A darker color could make each tile pop out. They should have grout sticks for you to play with to see which color you like the best.
Man,oh man I hope they have the skill to do this tile!