Matching colour between photos using the same area as reference point

[allo]

I have multiple profile pictures of staff members taken with the same backdrop, but due to issues with camera exposure, the colour tones of the images all look slightly different. Given the backdrop is supposed to be the same colour in all photos, is there a quick way in Gimp to use the backgrounds as a reference to match the “colour profile” of one image to another one?

Please help!

[Ofnuts]

Try this technique (matching the BG color and not the skin tones, obviously)