Decorating and Design - white tile what color grout?

We are redoing our bathroom. The bathtub, sink, toilet, cabinets, are all white. the ceramic tile is going to be white too. With all the different colors of grout available I need some suggestions as to what color to choose for grout to hide dirt, (so white is out) look good, not create to much contrast, yet remain neutral. Any ideas would be appreciated.

Are you planning to have any other colors in the room? What can look good is using your accent color. An example would be using green grout with white tile trimed with green tile on the edge. Or it could be towels or anything else that you could live with for a long time. Gray is another option. Taupe is a pink/gray. These are neutral colors and will go well with just about anything. I am not sure if grout comes in black but that could be a real cool look. It would be quite a statement if you go that way. A modern 50's look.

Well now the husband wants to go with black, but I always second guess him. No colors in the bathroom as of yet, want the walls to be full of color, but permanent things such as tile and countertops to remain neutral. Thanks for the ideas sometimes it just takes another opinion to be sure.