Paving Slabs

[tellytv]

I've had a builder lay some slabs, and when he done the pointing i'm pretty sure he's used the wrong sand as the joints stay real dark for days after it's been raining, as my old slabs dry out within a couple hours, does this look like the wrong sand thats been used? i'm not sure what sand he used.

http://i30.tinypic.com/eguw7t.jpg

I was thinking about knocking the pointing out and doing it again myself with this

http://www.awin1.com/awclick.php?mid=15 ... nvt/154003

do you know if the patio grout from wickes will be as strong as mixing it yourself? would you still be ablle to pressure wash the slabs down?