If you seal the grout before you move in, it will help. It's easier to keep clean if its sealed. I can't remember what I used on mine, it was years ago, but I think it came from Home Depot.
Thanks for the tip. I wondered if that was something the builders would do, so I'll ask them about it first. If not, I want to get some paint on Friday, so I'll ask what they recommend at the hardware store.
We asked our builders to seal the grout on our backsplash and they wouldn't - said it would void the warranty on the tile.