Our design team suggest you use Grout 26 Harbour Grey to accentuate the pattern colour.
Or to blend with the background use Grout 45 Mink.
Recommended Grout Joints - (We have assumed that your substrate has a perfectly flat and plumb surface, please check with your tiler.)
4mm grout joint. Based on this joint size, 1 bag of grout would cover 3.2m².