If you don't want to use Rubbish grout then checkout what brands people use on here by checking the
Adhesive Poll.
I'd go for Mapei, BAL and that myself. Never used the Palace gear.
Colourwise I'd go for Grey, I know its boring but it's the one that stays the same colour in high and low traffic areas. White would discolour and Black would fade over time.
Generally Ivory, Cream, Brown, Beige etc can be fine if you pick a good brand but if it's flexible the polymers used in them can whiten the grout as it cures... a problem reported on here somewhere.
So BAL Grey grout I'd be using. Superflex Grey if it's flexible you need.