I believe they color their synerlec additive so they can tell the difference between it and the PAO. If you go to their site and watch the video of the factory tour, you will see many containers behind the factory and inside that are colored purple or silver. They show samples taken when a truck arrives, and the fluid is clear as water. When they show the beaker in the lab, the clear fluid is spinning and they are adding purple additive using a dropper. I don't think they would be testing the dye color in the lab...