Grout Colour Problem: mapei ultracolour grout manhattan grey

[andywalker25]

Had our patio guys grout our porcelain patio yesterday and have to say to say feel quite unhappy with the result. The colour is really uneven and looks like a coating of white on some grey areas. The consistency of colour just doesn't look right. I've called them back to come take a look.

Has anyone experienced this before and what might have gone wrong and what the solution is?

A grout haze has also been left on the tiles which i can't seem to get off with mild detergent or with the pressure washer.

 

[Tile seller]

Ltp Grout Stain remover will get off the haze.
Sometimes, a light sanding of the grout will remove a top 'lighter coloured' layer.
If it does, then seal it