Cracked grout in the bathroom

Soubrette

I am now trying to sort out the bathroom floor (the ceiling looks fab though ). The wall and floor are tiled and I notice on another thread that posters would recommend putting silicone seal around the wall.

This was not done and now the grout between the floor tiles has a deep crack running through it. The crack starts dead against the wall but then moves to the other side of the grout in the tile so that the crack is against the tile.

Do I have to dig out the grout and regrout?

How do I colour match the grout? It is a light grey and looks almost like concrete - I bought the light grey from B&Q but it is a different grey and looks much more a solid block of colour.

Once done - should I seal around the wall anyway?

Thanks for your help

Sou