In a retrospective article detailing the making of Chapter 5, developer Toby Fox revealed that Seth was originally designed with lavender skin and white hair. The decision to revise this idea came about after his friends pointed out their resemblance to the character Amethyst from the 2013 American animated series Steven Universe. Concept art featured in the article showcases an early alternate design that features a uniformly white appearance barring a purple flower collar and a purple crescent moon decal on Seth's robe. A second design depicted in the same art features the same purple palette depicted in the final game, but retains the collar. While Seth's final design drops the decal and replaces their collar with a tie, the sprite based on the white design's pose features the tie curving into a crescent shape, alluding to this early idea.