The change of color for Ultraman’s Color Timer was done by replacing colored cellophane inside from blue to red.
Shigeo Kurakata in charge of gimmicks says the Timer was attached to the Ultraman suit with kite strings.
Almost everything must have been hand-made at that time.
Also, the expression of the Color Timer was possible because “Ultraman” was made for color TV.
In those days, most of the TV sets at home were monochrome ones, and color TV sets were spreading in Japan by degrees.
The production people were aware of it.
Also, they were expecting to export the SF drama “Ultraman” overseas.
But Toru Narita, Ultraman designer, did not like the Color Timer personally.
It is starange to have such a mechanical thing on the flesh.
That was what he said in later years’ publication.
In fact, Ultraman illustrated by Narita afterwards often has no Color Timer.
A dummy Ultraman with extreme perspective was used for the transformation sequence.
The dummy molded by Akira Sasaki, who was also in charge of molding the Ultraman mask, has no timer.
The Color Timer may have been attached to the Ultraman suit later than that in the shooting.
The time-pressured situation in preparation for shooting is imaginable.