How to keep the grout clean in light-colored tiles?

Hello,
we have now been living in a newly built rental property for 4 years. Now we want to have beige tiles again in our own house. Unfortunately, the grout, which was originally light gray, is now really black. Is there a tip on how to keep the grout in a newly built house light and clean for longer? (Brushing with a toothbrush yes, but you only do that once.)

Maybe there are some experiences here. Thanks to you.

Strange... the joints in our previous house still looked light gray (concrete gray) after 15 years.. the color did not change. They were also even wider than in your photo.

I also don't know that they turn black... Maybe a bit spotty - but that dirty? But maybe one could consider epoxy resin joints.

Hmm, the grout doesn't look dirty, just dark, and very evenly so. This probably isn't due to insufficient cleaning. Otherwise, there would also be lighter, patchy spots in the grout. Our tiler said years ago that you should never scrub the grout specifically with aggressive cleaners or brushes. Only then would cracks form where dirt can settle more easily. Our wider grout lines have only darkened minimally in over 15 years. No idea if this helps you at all. Layman's opinion, so take with a grain of salt.

I have found that this also depends on the grout, how much it darkens over time. With higher-quality grouts, dirt and residues from cleaners do not settle as easily. Friends used the cheapest one, and it became very dark and stained very quickly. Others had a tile setter come, and for the horrendously expensive designer tiles, he apparently used a corresponding grout – after now 10 years, they also look somewhat darker, but still "gray" and not blotchy. The first-mentioned friends with the now dark grout are rather the neat freaks. Therefore, I can really well imagine that it is primarily due to the quality. Unfortunately, I cannot (yet) tell you which grouts are particularly good – maybe other users here have long-term experience.

The grout is really dirty. I scrubbed a bit with the toothbrush. My wife often wipes, so it is the wet wiping that leaves residues. But it can't be that it only stays clean if you hardly clean it?