Hi. I'm not sure what colour you want but you can buy grout pens. Just google "grout pens". There are dark grey ones in Amazon with really good reviews

We've finally moved! We have a lime green tiled shower room where we've noticed a few tiles/grouting needs replacing. We've tried just re-grouting but it hasn't lasted (despite being left to dry). So.. can anyone please help us source these tiles please? (Mainly just the plain green tiles). Thanks all!

It comes down to personal taste doesn’t it? I prefer white tile with white grout as I think the grey grout has a grubbiness about it, rather like public toilets in the 1960’s and 70’s. Obviously if you are relatively young then you will not have this wonderful memory lol!

I too like the shiny white tiles in the photo. Although you made me look at them again after reading your reservations about possible associations with a 'gents loo', haha, but I don't think it will look like one. I think they can look great with a blue floor. In your photo it looks more like grey though.