Processing XCF files in batch

[Mate de Vita]

I have a large number (~3500) of .xcf GIMP projects. I would like to perform some simple operation on all of them. Specifically, the images all contain one layer that's all green and one layer that's all red, and I would like to flip those two colours (i.e. I would like to turn RGB (0, 255, 0) to (255, 0, 0) and vice versa).

Is there a way to do this automatically without manually opening each file in GIMP and recolouring it by hand?