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

https://www.hometalk.com/search/all?filter=clean%20grout

Hi Diane, this video shows all the usual ways to clean the grout, and the best, hope it helps you out

https://www.youtube.com/watch?v=PnmWAVRzfGc

The Best Way to Clean Grout-EVER!!! | Hometalk

https://www.hometalk.com/2295735/the-best-way-to-clean-grout-ever?expand_all_questions=1

https://www.hometalk.com/41693881/homemade-grout-cleaner-recipe?expand_all_questions=1

https://www.bobvila.com/articles/cleaning-grout/#.Wi6YzKZOmf0

https://www.hometalk.com/search/posts?filter=clean%20grout

The Best Way to Clean Grout-EVER!!!

Homemade Grout Cleaner Recipe

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:

https://experthometips.com/how-to-clean-grout

https://www.hometalk.com/31413513/make-your-grout-look-like-new

Good luck

Make Your Grout Look Like New!

Hello Diane,

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.