Below is a bracket that a customer asked to me for help on. As you can see there is a mis-colored part that cleaned up in stripping and then would reappear. This problem can be from a few things but his problem was from water hanging after the rinse in this location.
Water hang can oxodize the aluminum surface and change the anodize. I've had this problem in the past and solved by wiping the water and using compressed air to quick dry prior to racking. The aluminum will enter the tank dry.
Other problems could be contamination or casting impurities but not in this case. ***This dye is Deep Orange***