This was the first tokusatsu (Japanese special effects) TV series produced in color.
In the unaired pilot episode (which had since been available on home video in Japan; on a P-Productions pilot collection video, and the series DVD/Blu-Ray sets), Magma looked somewhat different from his established look in the series. The suit was more or less the same, but actor Tetsuya Uosumi instead wore gold makeup on his face, with the character's trademark long golden hair and antennae. This matched the look of the character from Osamu Tezuka's original manga, being able to emote. However, Uosumi's face often turned beet-red from stress. (He was also allergic to the gold makeup.) So instead, for the full series itself. he wore a golden face mask with white eyes and black pupils. The pilot version of Episode #1 has the initial look for Magma (with the shots replaced with the finalized mask look in the series itself).
Veteran voice actor Tôru Ôhira, playing the main villain, Goa, not only wore the costume/mask (with the bottom half of his face exposed, with makeup around his chin to match the monstrous mask), but also dubbed over his own voice as well. Apart from his voice actor work, as well as being the narrator on countless superhero shows (including Secret Squadron Gorenger (1975), Spider-Man (1978), Kagaku Sentai Dynaman (1983), and also Dinosaur Squadron Zyuranger (1992), which has been famously Americanized into Mighty Morphin Power Rangers (1993)), viewers may also recognize him outside of costume as Chief Kurata from another famous P-Productions tokusatsu superhero series, Spectreman (1971).
Premiered on July 4th, 1966. Aired 6 days before the pre-series premiere of the more popular series, Ultraman: A Special Effects Fantasy Series (1966) on July 10th. (The series proper for "Ultraman" premiered on July 17th.)
Originally planned as an anime series, this was one of the first projects that the studio, P-Productions, did entirely as a live-action series, but using their anime resources for optical effects. (P-Productions was an anime studio that, at the time, also did some visual effects scenes for tokusatsu movies and TV, including the classic Godzilla films from Toho.)