Even if the photos and videos were manipulated, what does that mean? It's not proof that they weren't beheaded. It just means the photos and videos went through post production.

Reliability is what matters with these things and making sure that you are reading it accurately.

Try to guess what was photoshopped here . Now this is how it looks without the photoshop. . So in short, there are normal differences in color that are to be expected in some cases.

Check these non-photoshopped images on http://fotoforensics.com and see what you get.

Just playing the devil's advocate here.