Aren’t most of those beautiful “pictures” actually false color?
Yes, I believe so.
Each color of light represents a specific frequency of the electromagnetic spectrum. In some of these cases the color is real but intensified to allow us to see them, as they are impossibly faint to the naked eye or even through a telescope. In other cases, totally false colors must be added in order to display any image at all. This is usually when the image is in frequencies other than normal optical light. Frequencies such as Radio, Ultraviolet, Infrared, Gamma, etc.
...some pictures are long exposure shots where the colors that ARE actually there build up over time and become visible. Others images are composite photos.