I think a classic dark grey grout for your lovely neo-traditional combination of tiles would make the most practical sense - white or light grey (or for that matter other colours of grout - say, yellow or blue) will get grubby on a floor, and, in my experience, black is (oddly enough) a bit of a nightmare to get clean as well (it also seems to get everywhere during the grouting process). That said, visually, I think a bright flash of, for example, sky blue would look striking and unusual. But you’d need to be prepared to scrub regularly... As an aside, have your floor tiles got a non-slip finish (or are they porous and not being sealed)? If so, take care when grouting to avoid getting them covered in grout and then having to go completely mad with grout remover after you’ve finished!

Thanks for the interest, we decided on dark grey ('graphite') in the end and I'm happy as I think it goes well with our dark grey cupboards. We will put a pale oak shelf above to match our floor and bring some colour in with plants etc. These are the tiles if anyone is interested. I tried about 8 samples of rectangle white tiles from both high-end and high-street sources but I love these as they are a fairly strong white but with the rustic texture. https://www.toppstiles.co.uk/artisau/artisau-gloss-white-tile?gclid=EAIaIQobChMIwoekh_LN7QIVlWDmCh1OmQAPEAQYASABEgIkIPD_BwE&gclsrc=aw.ds

Hi, we're re-tiling 2 bathrooms, both pretty small with showers. It's a small flat, so neither have windows, so no natural light. The flat is in Spain, so having vintage style floor tiles, just wondering what color grout to use. I guess the best would be like a darker off white, like the background color of the tiles, but I don't want it to get dirty after use and look awful. Or I don't want to create more cleaning than necessary for myself! You can see the floor tiles together for the pattern & then a photo with the wall tiles. What do you think?

Love those tiles! I think a mid grey or sage would be great. Too light a grey would make me think of dirty white lol. A stronger colour would make it really pop and be more modern in my opinion.