Can you darken grout after applied?

I have layed a light grey grout and would like to know if it is possible to darken the grout after applied to a darker grey? Without removing it and reapplying . It has not been sealed, it was just put down 24 hrs ago. Thanks.

Recoloring grout is possible. Go to a tile store (possibly big box stores also) and ask for grout stain in the color desired. Moving the color a notch or two may or may not produce splotchy results, but when the entire area is done it will not be too noticeable.