Tile grouting

[TheOtherHalf]

Weve had our bathroom re tiled about 2 months ago. Some of the grouting seems grey in colour rather than white. Its quite patchy too. The tiler says its just the grouting drying out as he had to plasterboard some of the walls after taking the old tiles off but its also grey on some of the walls that arent plasterboarded. He came back after a week a re grouted some of it but it still looks the same. We are getting used to it (but dont want to ) as people seeing our `new bathroom ` for the first time are bound to notice it. He is quite willing to come and re- do it again if its still the same in a months time. Has anyone else experienced this as he says it has happened before but dried out eventually
TIA

[flitty]

Lakeland plastics sell a grout whitener that really works. Use it like a shoe whitener.They do different colours. Mail order or one of their shops

[TheOtherHalf]

Thanks, will look into that, but I really think he should solve the problem, dont you.
Sorry Ive posted this twice as I wasnt sure which heading to put it under