Varying shades in older tile can make it easier to find a replacement.
In an ideal world, everyone with floor tile would have a stash of extra tiles handy for replacing damaged ones. If you aren't lucky enough to have matching tile handy, you can still replace a broken or damaged tile with a new one that will blend in with the old ones. Older tiles were commonly 12-by-12 inches, rather than the larger 16- and 18-inch tiles currently popular.
Look at the tiles surrounding the one to be replaced to determine whether the tiles are uniform or have variances in the color and pattern. For example, the floor may appear to be a solid shade of brown, but a close look at the tiles may reveal that the color varies slightly from tile to tile, or even within the same tile. Lift or chip out a piece of the tile to be replaced. The piece should be big enough to see and match the color and pattern. Note the thickness of the tile. A thinner tile can be used to replace it by building up the mortar underneath it, but a thicker tile will not be flush with the existing tiles.
It may be possible to match tiles that are a solid color or have a classic pattern at your local home improvement store. Take along the chipped-out piece of the tile to find a good match. Even what looks like a basic white tile may come in several shades of white, such as bright white, ivory, cream, bone and off-white. For tiles that have unusual or vintage patterns, or an uncommon color, check stores that stock antique, vintage and older tiles, including online sites that specialize in matching older tiles. There are also a few manufacturers that will create custom tiles to match existing ones, but it can be expensive and may not be cost-effective for replacing a single tile.
If you cannot match the older tiles exactly, or it is not cost-effective to do so, consider creating a pattern with new tiles. For example, if the tile that needs to be replaced is near the edge of the room, create a border or checkered border with new tiles. If it is in the center of the room, create a focal point with five or more tiles in a checkerboard pattern -- either solid or with designs -- so it looks like an intended decorative element.
Get ready to take out the old tile by covering any nearby objects that could be damaged by flying pieces of tile, such as a porcelain bathtub or wood furniture. Wear gloves and eye protection. Remove as much of the grout around the tile as possible, using a grout saw. Tap the center of the tile with a hammer and chisel until you create a small hole in the tile. Continue chipping away at the center until you can pry away larger pieces. When all of the tile has been removed, use a heavy-duty chisel to chip away the mortar underneath the tile. You do not need to remove every bit of mortar, but make sure the surface is level and the remaining mortar is securely attached to the sub-floor.
Apply a thin layer of tile adhesive to the back of the new tile and press it into place. Allow it to dry overnight. Meanwhile, spread a thin line of grout on a scrap piece of cardboard or heavy paper and let it dry. Place it next to the existing grout to see whether it matches in color and texture. When you've found a match, use a putty knife to push the grout into place. Smooth the grout lines with your finger and wipe away any excess with a sponge.
Jones, Carlye. "How to Match and Replace Older 12-by-12-Inch Ceramic Floor Tiles." Home Guides | SF Gate, http://homeguides.sfgate.com/match-replace-older-12by12inch-ceramic-floor-tiles-102258.html. Accessed 21 April 2019.