Our design team suggest you keep it simple with Grout colour 6, light grey as it blends so subtly with the tile.
Or if you want a lighter touch to bring our the warm tones use colour 43 Sand stone.
Recommended Grout Joints - (We have assumed that your substrate has a perfectly flat and plumb surface, please check with your tiler.)
3mm grout joint. Based on this joint size, 1 bag of grout would cover 19m².