Promising review: “Holy cow! I never thought my stained grout would look so good! These pens are so amazing. After a little priming, they go forever! They cover very well and are super easy to use and cover the darkest of stains! I am buying four more to cover the rest of the house. The tip does not get into the very end of a line due to the border, but I prime it a bit for excess paint and push it in with my finger. Also, this is great for those deep small holes or grooves that are in the tile that leave dirt spots that are almost impossible to get out. Just prime it over the hole and rub it in with your finger and wipe off the rest. I have very light beige tile, and the beige color pens blend perfectly. I would NOT recommend white unless you have very white tile. This beige will blend well with white as well. Cannot beat it for the price and the amazing job this pen does. One pen will cover about a 3×20-foot area, no problem.” —NatJH

Get it from Amazon for $8.99+ (available in two sizes and in additional colors).