I have ceramic tile in a lot of rooms. The grout was the hardest part to get clean as it was lower then the tile squares. The grout always looked darker in spots. I had the tile guy come and regrout until the grout was just shy of being level with the tile. Now it's a lot easier to clean when mopping. It's been over 5 years and the grout looks fine. I had to do a lot of explaining to the guy what I wanted, he wanted paid so he did it. LOL