Tile comes in a variety of color, textures, and finishes. The variation in color and texture should be intentional and not accidental.
As seen in this image at the right the variation is moderate. This variation should be known ahead of time before installation and it may or may not be acceptable to you based on your original choice of style.
Tile manufacturers and retail stores can inform you about the actual variation of any specific tile. Sometimes the manufacturer indicated the level of this variation on the box of tile. Also you could open a box of tile and spread out several pieces to get a better look.
Before accepting delivery of tile from the store, check that the shade and tone serial numbers match on every box. Look at each box of tile and locate the shade and tone label. As seen in this image there are many numbers and data but somewhere there should be a specific mention about shade and tone.
It is essential that every box of tile shares the same exact shade and tone number. This indicates that these tiles have been manufactured to the same color and quality specification and thus should share the same color qualities you saw when choosing the tile.
The extra step in the quality assurance process is examining each tile from the boxes and sorting out any defective pieces. Besides color issues you may find tiles with surface blemishes or minor cracks that you might otherwise overlook during the installation process. Don't discard or returns these tile just yet. These pieces may be used as cut pieces if the color is within specification.