Flybox
I think your grout color was a good choice. It looks great. I will usually wait about 1/2 hour for the grout to set up to the consistency of cheese before I wipe it down. Use the float to get the tile as clean as possible as you want to keep the sponging to a minimum. The more you wipe it with the wet sponge the more the grout will effervesce leading to color changes and a light colored residue. It's a fine line and I will often pick a color one shade darker as it often ends up being a bit lighter than the sample. I don't use the Home Depot Polyblend grout as it seems to be one of the worst for effervescing.
I also like to layout some tiles dry on a board or cardboard and spread some dry grout into the seams and get a better idea of how it will look. Another thing you can do is to coat the tile with grout/tile sealer before grouting and this will help with final cleaning. Not so much with glass but stone or textured tile it will be a big help. Just don't flood the tile as you want to keep it off the edges.
Another thing I do, and not everyone does this, is when I have a transition to different surface I use a matched latex flexible grout for that seam. Like between the counter top and the bottom row of tile, or between a bathtub/shower pan and floor. The grout here may eventually hairline crack due to movement in the cabinets/countertop. Don't bum out if you did not do that...it's not a huge deal and may never be a problem...it's just something I do.
Transitions to another surface or material sometimes need a little time in the thinking chair to pull off. I had to tie in wainscoating in the "blue" bathroom.
