Each manufacturer will have their own tone of colors. The same manufactuere will have a difference in tone from year to year. Each batch that is made is uniform, but if the mixture changes in the manufacturing process, the tone will change with it. Color Tones also may change in porcelain compared to acrylic. So, the acrylic tub may have a difference color tone than your pedestal sink or toilet.
It would be hard to say what sort of color difference you would see when the fixtures are side by side.You may not even notice any difference
The best set up is, to buy all the fixtures from one manufacturer , if you are worried of possible color changes.