This is called a shade variation issue. When you floor the tile sometimes you observe different shades even the tile is from the same design. To understand the problem first we need to understand that tiles polishing are 2 types... - body tiles (soluble salt, double charge, full-body, twin charge, etc) - glaze tiles (GVT tiles, ceramic wall or floor tiles) There are always more chances of shade variation in body polishing tiles as the tile body is directly exposed to the surface. Many times in the same batch two shades are observed. For glazed tiles, shade variation can happen only in two different batches. As an end-user, you first do a mock-up of the flooring. If the shade variation is observed take pictures and ask the supplier about it. Don't fix the tiles in the same area (room) which is having shade variation.