The tone you choose for your kitchen grout depends on the design you're trying to achieve. If you want to emphasize the pattern of your tile, it's best to use a contrasting color. If you're looking to unify the tile with a tiled floor that looks like wood, opt for a similar shade that is slightly lighter than the tile. The grout can be lighter or darker than the tile, or the same color.
When selecting the color of the grout, take into account the color, pattern, shape and design of the tile and how the color of the grout will either enhance or detract from these elements.