Hi joanna, hope this helps you out, also once you get it cleaned, you may want to seal it to keep it clean,

https://www.fromthiskitchentable.com/clean-grout/

Hi Joanna,

You could scrub them with a nail brush and when dry paint them over or Using a Dremel cut out the grout and re-grout maybe.

Hi Joanna,

I've trusted Hunker.com for many years for good advice. This article will give you some ideas of what you should and should not do with dark grout. Deb K's answer to seal it when it's clean is also a good tip. Wishing you the best.

https://www.hunker.com/12324305/how-to-clean-colored-tile-grout

1. Prep the area: Begin by spraying the grout with hot water and scrubbing with a stiff bristle brush (an old toothbrush is perfect for this) to remove any dirt or grime on the surface. Follow the grout line as you spray and scrub in a circular motion. If you have one on hand, you can also use a steam cleaner, which is very efficient at cleaning grout.

2. Mix the cleaning solution: Make a grout cleaner paste of two parts baking soda to one part hydrogen peroxide. If you’re working in an area where grout is exposed to grease (like in the kitchen), add in a few drops of dish soap.

3. Apply the solution: Spoon the homemade grout cleaner onto the grout lines and allow it to sit for around 10 to 15 minutes. Giving the cleaner time to work into the pores will result in cleaner and brighter-looking grout.

4. Start scrubbing: Using a brush, scrub the grout lines to lift up any dirt trapped in the pores.

5. Rinse the tile: After scrubbing, mix a few drops of dish detergent in with some hot water and use a sponge or cloth to rinse the tile and wipe up the remaining grout cleaner.

I would paint them the color you would like them to be and then use a grout sealer to protect it and make it way easier for cleaning in the future.

The cleaning suggestions from Mogie are comprehensive. You could also remove and re-install new grout, then seal. There are some grouts out there that don't require a sealer. We have that in our grouted areas. An oscillating tool and grout removal blade can be used to remove the grout.

Use a mixture of hydrogen peroxide and baking soda. Apply mixture with an old toothbrush in a circular motion. Let it sit for 10 minutes. Rinse well with water and dry. If I were you I would use apply several coats of 511 Spray-On Grout Sealer once the grout is completely dry.

At home depot and lowe's you can also buy grout cleaner and sealer - you clean the grout first let dry the seal it...

Hi! maybe this will help

https://www.flooringinc.com/buyers-guide/how-to-clean-and-seal-grout.html

Hi Joanna: Check these sites for some ideas:

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

https://homeguides.sfgate.com/touch-up-grout-20644.html

Good luck

Make Your Grout Look Like New!

This homemade cleaner will help: https://www.youtube.com/watch?v=ifeSybjr2RY&t=8s

The grouting may be too far worn down to stay clean. It sounds like it will need to be resealed again after it is cleaned and dried, as others have already mentioned.

Clean with a degreaser first. If that doesn't get it done, use Lysol toilet bowl cleaner that comes in the black squirt bottle.