try this: https://www.craftylittlegnome.com/the-best-homemade-grout-cleaner/
You can make your own homemade grout cleaner! Mix together 1/2 cup of baking soda, 1/4 cup of hydrogen peroxide, and 1 tsp dish soap. Apply cleaning mixture onto grout, wait 5-10 minutes, scrub and rinse.
Mix a half cup of baking soda, 1/4 cup hydrogen peroxide, and 1 tsp of dish soap. Apply to grout and let it work for 15-20 minutes. Scrub with an old toothbrush and rinse.
Here yah go
Hi Diane, this video shows all the usual ways to clean the grout, and the best, hope it helps you out
The Best Way to Clean Grout-EVER!!! | Hometalk
I use a soft scrub mixture of baking soda and water to a paste consistency. Let it sit a bit and scrub it off. Dingy? Add hydrogen peroxide to your paste. If it isn't sealed, once you have it clean again, I would seal it. Good luck and stay safe!
Hi Diane: Here are some sites that are sure to help:
You could use bleach on a toothbrush,(be careful to shield your eyes from splashes) or if not bad use Toothpaste or Barkeepers friend. Otherwise if all else fails - paint them with an Artist brush and Acrylic paint............Good luck!
I clean my grout and tile floors with vinegar - https://chascrazycreations.com/natural-cleaning-with-vinegar/
I scrub with a toothbrush
Hi Diane, You can make a thin paste of hydrogen peroxide and baking soda. Apply it to the grout and let it sit for about 10-15 minutes. Scrub with an old toothbrush and rinse clean. If the grout between the tiles has worn down too far, it may be a better idea to first re-grout and then seal. You can also buy grout pens to quickly “recolor” your grout and make them look new again.