Old dirty grout

Best thing I've found is CLR Bath & Kitchen Cleaner. Yellow spray bottle found at Walmart. Spray it on, wait about 5 min., brush with an old tooth brush, rinse off with sponge. You may have to use it a couple of times.

Here are a couple links for you. Once it is sparkling clean again, I would seriously consider resealing to make future maintenance easier.

http://m.wikihow.com/Clean-Grout-Between-Floor-Tiles

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

a steamer with a pointed nozzle is the best thing I've ever used

After thoroughly cleaning, you can stain or paint your grout. There are special products to buy and should be at big box hardware/DIY stores.

I squirt hydrogen peroxide on them and srub with a toothbrush or bristle brush and then wipe it up with a warm rag . Works great!

thanks everyone!

Sure can! I've used it on all colors from white to dark brown.

thank you

ok this sounds weird but works toothpaste!

Thanks everyone. Great ideas.

I made an Oxy Clean paste with water and scrubbed it with a toothbrush. Wiped it off with a damp rag. Cleaned it right up. Forgotten how blue my grout actually was! Then sealed it well.

Make a paste of baking soda and peroxide then apply it to your grout with a toothbrush. Let it sit a little and then remove with a clean cloth.