Hi, I have white ceramic kitchen floor tiles, which I put white grout in 18months ago, this grout has become stained,dirty, and will not clean, I have tried allsorts, so I thought I would change the grout to Grey, will I have to remove the white grout or can i put the grey on top of the white, there is quite a deep ridge between the tiles, the grout is not flush with the tiles. A x x
