Just had some porcelian tiles laid in the hall, large ones but don't look at the colour of the grout before the tiler used.

It's like yellow and looks pretty bad, any thoughts as to a solution?

Is a scraping job and re-grout?

Sounds that way. I know this is hindsight but I take it the tiler choose the colour

Only propper way is to rake out all the grout as much as possible then have it grouted again with a colour you like.

Grout can be raked out quiet easily, though time consuming with a standard grout rake bought from any tile shop, and requires pleanty of arm work, or the more expensive but faster way is to get hold of a Fein multimaster type of tool.

Best option is always to check the colour of grout before having anything tiled

No I did, just went into B & Q, they had black, grey, white and sandstone......

I got sandstone and its yellow

A tile shop will have a greater range of colours, take a tile with you, where are you based

B &Q, it was probably bagged and packaged as black!

I raked out previous grout easily with a Dremmel. Make sure your get a tungston 'bit'. Downside lots of dust!!!