When the shade of two pieces of carpet vary from each other when they are supposed to look the same. It’ can be very difficult to spot this until both pieces are rolled out side by side. Different hues will really be noticeable with a side match issue.
When the fibers are being manufactured, the dye can vary between mixtures, so that the difference between that roll and the next can sometimes be significant. Because of the many-step processes to make carpet, it is possible for color variations.
To inspect for side match problems, a flooring inspector would look closely for variations in the color. They would need to check out the pile-lay on each of the carpet panels in question. Other things they would do would be to check out the surface texture of each pane on both sides of the seam to make sure there is even tension. All these precautions should be enough to eliminate a real side match appearance in a carpet.