Refreshing bathroom tiles

[franglais]

I'm giving my bathroom a makeover, and want to clean up the existing wal tiles. They're 60mm light blue in colour with white grout between. I say white grout, but it's turned a nasty grey colour and I want to whiten it or replace it. I tried scraping out the grout, but it is rock hard and I'm afraid of chipping the tiles. Any suggestions how I could either soften the grout to help its removal, or whiten the grout without further removal?

 

[Zampa]

Make up a 50/50 solution of bleach and water and use an old toothbrush to scrub the joints then leave for a day....then rinse the whole wall down

 

[sandwell]

I have found Flash gel with Bleach does an excellent job. The gel will cling to the grout long enough to bleach it, then wash it down with an old toothbrush. Scouring powder with bleach also is effective.