First of all, this is a fictionalized story of a fictional private investigator hired by George Reeves’ mother to look into the son’s death. The film does use Reeves’ biographer as a consultant, so the aspects that are portrayed about Reeves’ life are more or less truthful.
The Adventures of Superman aired on television from 1952 - 1958, 104 total episodes, of which 52 were in black and white and 52 were in color. You do get to see Affleck, who is playing Reeves wearing both Superman costumes used during filming.
For the black and white filming, they used a light gray instead of blue and dark brown instead of red for better contrast detail. Of course for the color filming they used the standard red and blue.
The film does show some of the filming the show process, not much, but does recreate one famous near disaster, when Reeves was being filmed flying using a wire harness and the wires break and he crashes 12 feet to the floor. After that he refused to use the wiring harness and they had to come up with a new way to film his flight scenes.
Reeves did not like the part, he felt it was beneath him and only did it because he could not find any other parts. He was out of work and depressed about his career at the time of his death and the film explores many possible scenarios as to how he possibly died. It leaves it up the viewer to form their own opinion as to which one it was.
It is a good film, but do not go and see it thinking you will see much Superman footage, he is seen in the costume a total of 8 minutes or less.