use some grout stain its really easy to use worth a try rather than going to the effort of channeling around evry channel to get the old grout out. it does work i have seen the results from my old man. you can get it in all sorts of wierd colours aswell if that takes ya fancy. failing that try tipex lol
hi Eva spraying bleach or mould or midew cleaner are ok but its better if you do it the hard way it will last longer . for me clear the old grout out[which you can get a tool from b&q cheep] and then regrout .
it's not that bad, just kinda off white rather than white. i will give the vinegar and bicarb or bleach a go first, if that doesn't work i will try chris's suggestion. don't think i am going to regrout anyway.