How do I renew the grout in my bathroom?

There is a product called Grout Renew at our home improvement, Lowe’s, not sure where you are or who you would havw, it is painted onto the grout lines and makes it look brand new. We have a 60s house with the white square tile in the bath, tried EVERY learning theory out there! it is a little tedious but the results are worth it

Painting it can be a little tedious, but it works! Here's how I did it: https://thehoneycombhome.com/painting-grout-how-to/

That looks great. I am going to try it. Thanks for the info

Ok unconventional but I’ve used it on floor grout. Try in a small area to test first. It’s VERY strong. Spilled it on living room carpet and it melted it. Work in small sections with rubber gloves and window open if possible and rinse well. The Works toilet bowl cleaner. Old original thin one. Couple bucks at Walmart and works on true grout not that rubber sealer. I paint on grout lines with sponge paint brush. Let sit for 3-5 mins. Use a stuff brush to scrub grout lines then rinse. If it doesn’t work you have great toilet bowl cleaner and are not out any money. I used to have a toilet that had so much iron in the water and was always orange. This washed it right off before using a brush and other toilet cleaners had no effect. Also removed spray paint off brick from my toddler getting into stuff. I tried every paint remover imaginable then this and it worked. So if all else fails I bring out my ‘big gun’ The Works tb cleaner 😂

Thanks for your reply.

I painted mine with an easy to use paint pen I found at Home Depot. It was inexpensive too.