We strongly recommend that you use our Mapei Ultracolour PLUS grout on all your stone installation products. This lightly sanded grout will not harm polished marble, limestone and travertine during the grouting process. The sand component is relatively fine to cause any harm. There are many colours to choose from. Readily available colours are: White (100), Manhattan (110), Grigio Cemento (113), Anthracite (114), Nero (120) & Beige 2000 (132). Kindly be aware that some very porous stone types will require pre-sealing before grouting. Mapei is a world reknowed brand for tiling adhesives, water proofing, primers, etc..