Grouting up to a different exsisting color

I've pretty much completed my shower stall tile installation. Since I was limited in the tile from the existing floor I used the same floor tile as the entire bathroon into the shower and then changed to a different contrasting tile to do the walls. I used som accents from the floor in the walls to pull it together. The pproblem is this.
I wanted to use a dirrent grout on the floor of the shower than on the walls. Can this be done without making a mess.

Yes.

Do one, let it set overnight, then do the other.

Thanks RD. Is that it? Im thinking I would like to grout the shower floor and the curb with the darker grout that is throughout the bathroom floor and then go with a much lighter color on the shower walls. Any masking? Or precautions? Wont some of the dark grout from the shower floor work its way into the vertical grout lines of the wall tile at the floor/wall interface. Am I just being paranoid? I dont want to botch a great tile job at the end.
Thanks for the help
Dmc

Tape off the area that you want to keep clean and cover the rest of the floor from grout dropping on it.

When finished and before it sets up, remove the tape from the floor at the wall joints and clean any excess grout that might have bled under the tape.