To make Vash's appearance distinctive, Nightow often changed the character's hair color throughout the serialization. Although fans questioned if this was relevant to the story, Nightow chose not to reveal his reason for it. In the series' climax, it is revealed that Vash's blond hair turning black is a secondary effect of overusing his supernatural powers. Despite his efforts in his design, Nightow regrets giving Vash and antagonist Legato Bluesummers detailed eyes because he drew them inconsistently in the manga. Nightow had trouble designing Vash's gun as he aimed it to look visually attractive and effective to use. Although he originally wanted to create a gun with unlimited bullets, he replaced it with a traditional one after consulting a picture of an upside-down barrel for inspiration. Besides Vash's guns, Nightow portrayed him as having a supernatural power known as the "Angel Arms," in which his arms mutate to form a weapon. The Angel Arms adopt a feminine form and can create or give birth to matter.