The grout may be lighter in the morning. Usually it dries lighter than how it first appears.

Thank you. I think the real problem is the tile guy's smaller spacer was twice the size of the spaces on the demo at the the tile showroom and I didn't realize this. As a result, there is more grout to see. I spoke to the tile company this morning and they've told me there is a lightener, so all is not lost. Any thoughts about lightening grout would be much appreciated.

Don't do anything to the grout until it is dry-which can take quite a while.

Thank you. Our question is how long to wait? It has been 24 hours

You can stain the grout as long as you don't seal it first - and as long as it is not epoxy grout. You would order a grout stain the color you want and you paint it on with a very small artist brush. Clean any excess as you go along. The stain is also a sealer so you don't have to seal it when you are done. Before you try to cook or wash the area (or do anything that would affect the grout) wait several days for the stain to dry. Depends on what type of grout it is. Most grout dries in 24 hours.