According to Tetsuo Yamamura, the costume was found painted light purple (fuji-iro=wisteria color) when it was delivered to the set, and he says it was very much beautiful. He states the repainting work was done by the staff from the art section of Tsuburaya Productions as repainting often happened to kaiju costumes delivered to the studio.
The set where Gyeron appeared with flowers in bloom all over the field and a stream meant to be a river flowing was fantastic, and I am fully aware that the use of the fluffy stuff coming out of the wing torn off the body was a considerate arrangement not to show blood to kid viewers along with the yellow blood spewing out of the kaiju’s throat cut by Ultraseven with Eye Slugger held in his hand that looked different from real blood.
Nevertheless, the scene of having Ultraseven tear off Gyeron’s wing could have been too cruel, and there seem to have been some children who thought along with the sympathy they felt for the stellar beast, “Oh, stop it, Seven! That’s enough!”
I myself find the scene a bit repulsive when I watch it now, but this episode featuring Gyeron is very much thought-provoking at any rate, and it could be one of the reasons that “Ultraseven” is often described as the series “worthy of appreciation by adults” although I personally don’t like this hackneyed Japanese cliche very much (also wondering if it makes sense in English) as I heartily admire Tohl Narita’s attitude while he put it as “the show to be watched by children makes the work even harder because you can’t fool them.”