I have about 1500 sq ft of 12x12 floor tile in my house. It was by a previous owner so I don't know how the grout was treated. The grout is a light gray (Portland color). The grout in the traffic paths has darkened and there are darkened stains. I would not mind darkening all the grout but would like it even and then seal it. I would steam clean it and seal it but I am afraid the stains will seep back from deeper in the grout. Any suggestions would be appreciated.