Hello new friends! I'm in the final stages of pool completion, currently I have all tiles in place (glass irridescent mosaic, also irridescent subway tile) for waterline & benches etc. however the grout suggested by our pool contractor, that he has been using for many years on countless pools with good reasoning as to why this product is the best choice. eg. it's able to be re- grouted also cleaned via diluted acid wash. Q. The grout color is black (witch he has not used a great deal in the past) my concern is if washed with acid could it bleed down into the plaster thus staining it. the product is also a concrete base. without recomending to apply any sealant, do to pool chemical effects to sealants. anyway can anyone suggest a suitable grout for the color black with the best resistance to pool water etc.