Flooring Tile - New type of grout--not so sure

I bought Polyblend polymer-modified, sanded grout in a bone color. I mixed it last night and floated it in, that was all fine. Tonight when I got home, I noticed that there are a few (very few) places that the grout color is much lighter than others. I was VERY, VERY careful to wipe the excess grout with a BARELY wet tile sponge, since I hear that excess water can allow the grout to change colors and also to crack or chalk up. Even with that, I still got some lighter spots here and there.

Do you think I used too LITTLE water when I mixed it? Is it possible to get it too dry? I felt it floated just fine but I did try to squeeze it from a grout bag at first. That proved to be a tough chore, and I switched to pressing it down in the cracks with my grout float? Also, the other grouts I have used said I could seal the next day, this one recommends "lightly misting the grout" for three days. I think I need to hear from the "experts" on this one.

Give it a little time, it is basically curing concrete, for lack of a better term. Follow the instructions and mist it tomorrow. If it's a floor wait a good week to seal it, the moisture in the grout and thinset need somewhere to dissipate. Too little water is a doubtful cause for light spots. I mix my grout pretty dry.

OK, sounds good. I spread the grout last night so I will mist tonight. I was kind of wondering why, and assume that by misting, the grout doesn't totally seal over on top before the bottom part cures.

Or, maybe the answer is just................"because that is how it is done."

Thanks for your quick response, I appreciate it.