I have a dark floor grout that I put down last week, but there is still a white haze that I can't seem to get rid of. I have wiped it down a few times and when it's wet it looks good but as it dries it dries really white ....

Is there a trick to this? Or, when I seal it will the dark color show better?

It's a Mapei Kerecolor Sanded Grout, "Charcoal" if anyone has experience with it.

Thanks

Try a water/vinegar solution 3:1. That usually takes the haze off. If it doesn't you may have to move to something stronger.

I just used that same grout a couple of weeks ago. Didn't have any haze issues. Sounds like you had a little too much water on your sponge during clean-up.
My problem with that grout color was that it actually turned out much darker than the Mapei grout sample.

The grout color won't change unless you use an enhancer to seal the grout. Most regular sealers will not darken the grout, but you should test the sealer in an inconspicuous spot first.