Choosing the right grout color can change the way your whole tile project looks. The grout color helps tie in each tile to appear as one complete floor. The function of grout is to protect the edges of the tile from being chipped or cracked. When trying to choose a grout color, it is helpful to look at the sample on all four corners of the tile, preferably in the space where the tile will be installed. It is also helpful to place several different colors near the sample you are considering. This can easily help rule out some colors while making some colors a clearer choice.
When choosing a grout color, there are several different approaches you can take.
Blend - Choosing a grout color that compliments or almost matches the tile will make the floor look more 
even and uniform overall. In this case, the grout almost disappears. The way I look at it is, you paid for the tile and not the grout, so let the tile stand out instead of the grout. Don’t worry if the color doesn’t match exactly. As long as it blends and is in the same family, you are ok.
Contrast - Contrasting grout is sometimes a desired look, but will make the floor appeared more checkerboard. This is unavoidable when intentionally choosing a checkerboard pattern tile. When using a multicolored m
osaic tile, you can’t possibly choose one color. In this case, a contrasting grout can simply serve as a neutral background. Choosing a specific color could change the overall color appearance of the mosaic.
Accent -With today’s popular styles of tile, they are no longer a solid color. This can make choosing grout a little bit more challenging. Often, these tiles have a lot of range of color. In this case, any color grout that matches or blends with the family of colors in the tile will look great. Sometimes, there will be a more solid color along the edges of the tile. In this case, you can choose to highlight or accent that color by choosing a grout color similar to the color along the edge. This will make that border more visible. Most of the time, it is more desirable to choose a color with in the color ranges of the tile rather than the color on the edge of the tile.
Another way to accent with grout is to intentionally use a color that is not in the floor tile, but perhaps the wall color. For example, a black and white checkerboard floor can have a deep red grout to compliment red walls or red accents in the room.
Things to consider:
- White grout can be bleached and should mostly be used only with pure white tiles
- Light colored grouts should be sealed in heavy traffic areas
- Darker colored grout hides more dirt
- Dark grout can fade from sunlight and harsh cleaners
- Sealing grout can help protect the color as well as provide protection from mold and mildew
- Epoxy grout keeps stains from penetrating the grout, more so than a sealer and does not need to be reapplied. It’s great for countertops.
- Faded or discolored grout is not ruined. It can be re-stained.
- Different grouts are needed for different jobs. Unsanded grout is used for smaller grout joints such as natural stone joints. Sanded grout is used for normal and larger grout joints. Mexican tile or Saltillo has special grout for it’s larger than normal grout joints. Your flooring professional will guide you on what to use. For DIY projects, check the back of the bag for more specific instructions.
- Areas where a tiled surface meets a perpendicular surface should be caulked and not grouted. This may require you (not the tile setter) to recaulk annually in areas like the where the wall tile meets the bath tub or where the countertop meets the backsplash.
- It is always a good idea to keep grout from the original installation in case of repair. Grout from a later batch might not match exactly. If a repair happens and your new grout doesn’t match, remember you always have the option of staining the whole floor to a uniform color.
Another Green Build Expo find: 
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