There are grout colorants, which are epoxy based used to change the color of grout. Maybe that is what is meant by the latex paint or maybe they in fact did paint it with latex paint?
If they used a grout colorant and it was applied correctly it should be able to withstand cleaning. Maybe they used some type of paint that is attracting dirt? I would not use high pressure cleaning unless it was in a commercial kitchen or an industrial application. The best way to clean a tile floor and the grout is to use an appropriate bristle brush on an extended handle so you can scrub standing up (do not use anything that will cause scratches). Use an appropriate tile and grout cleaner (visit www.CTaSC.com resources and links page for links to the websites of cleaners and sealers manufacturers). Avoid acid based cleaners. Add the cleaner to your water and wet and scrub the tile and grout. Use a wet and dry vacuum to pick up the dirty water. Rinse the floor again if necessary and pick up dirty water with wet and dry vacuum. After the tile and grout is dry and is as clean as you want it to be, then apply an appropriate penetrating sealer over the tile and grout. Within 5 minutes of
