In article .com, "Richard" wrote:
Now two weeks later there are places on the floor where the grout is
still gray instead of turning white. Maybe 10% or so of the grout on
the floor. Some scattered around the floor, a few places where there
are lines of gray. All the grout feels hard, even the gray stuff.

Then it's cured.

I still haven't sealed it, hoping it will finally dry out.

After two weeks, it's as dry as it's going to get.

Has anyone ever seen something like this happen?

Different brands of grout, or even different batches of the same brand, can be
different colors. Also, using too much or too little water in the mix can
change the color slightly -- not much, but enough to be noticeable when you're
seeing them side-by-side.

Am I going to have to regrout
the floor?

You might be able to bleach to gray parts...

Or, curses!, have to call someone who actually knows
something about ceramic tile.

... but this sounds like your best bet.
Any suggestions or experience will be appreciated.

Thanks,
Richard