Godzilla's burning form could have had a much different look in his final battle against King Ghidorah in Godzilla: King of the Monsters, as the special features in the home video release of the new movie shows that the fire on Godzilla's body could have been blue instead of red.
In Godzilla: King of the Monsters, Godzilla was nearly killed by the Oxygen Destroyer, before being brought back to life by the efforts of Dr. Serizawa (Ken Watanabe). In the movie's final showdown, Ghidorah pushed Godzilla to his limit, forcing Mothra to make the ultimate sacrifice. Mothra's death fueled Godzilla with energy, and that energy caused him to enter his burning form. With his newfound power, Godzilla easily overwhelmed Ghidorah and destroyed him with two atomic pulses. After eliminating "The False King", Godzilla was once again the King of the Monsters.
One of the special features on the Godzilla: King of the Monsters Blu-ray, "Godzilla 2.0", goes into the thought process behind creating Godzilla's burning form. The featurette reveals several early designs for his fiery new look. Some of these images had Godzilla with significantly less lines all over his body, and others toyed with changing the color from red to blue. One in particular saw Godzilla covered in blue lines, from head to tail. If this was the chosen design, Godzilla would have had glowing blue energy bursting from his veins, mouth, and eyes. The reason why this design was rejected is never specified.
This look would have been drastically different from the one that made it into the final film, which at least resembles Godzilla's original burning form in Godzilla vs. Destoroyah, where his body was covered in red patches. The same cannot be said for the blue version. It's worth noting that while Godzilla's blue form may not have been as visually spectacular as the red version, it still would have made sense, considering that Godzilla's atomic breath is already blue. What happened to Godzilla would have looked less like a transformation, and more like a power-up in that case.
Of course, that could be the very reason why it wasn't in the movie. The scene of steel melting as Godzilla stepped forward, blazing with red fire, was one of the most thrilling moments in the sequel. For this scene, it was important that Godzilla looked as powerful as ever, as this was the moment where he demonstrated to Rodan and all the others Titans that he was the planet's true alpha predator. Plus, what Mothra did wasn't simply power up Godzilla but truly transform him into something else, a form that was considerably more powerful.
- Godzilla vs. Kong (2020) release date: Mar 13, 2020