Bought some lovely big slate tiles for a new patio and husband spent ages laying hardcore and leveling, and laying them. The disaster is the mortar. He bought brick mortar and now we have beautiful blue/black slate tiles and brown mortar. He's done such a brilliant job I could never say we need to pull the mortar out - first patio he's ever laid and it looks amazing. Is there anyway to paint it grey?????? Brown is truly horrible.