A wonderful thing in the 1800’s brought “Interchangeable Parts,” in which seems like the case for the different colored engine cowlings. An aircraft might receive wear on it’s engines and require a new one from a different aircraft. Nose cones are also a common thing you might see be mis-colored.
As other said this is due to parts of aircraft with different livery versions being swapped. Sometimes an aircraft part gets replaced and the original one gets repaired/stored until another aircraft needs that part. That’s how different colored parts end up on aircraft.