Purple is used as an accent color in the Ghost Zone.
"I love all the purple in the Ghost Zone," Chelsea said as she looked through photos on her computer. Danny, Tucker, Sam, and Jacob were in her room with her.
"Aren't you supposed to be doing homework?" Jacob asked.
"I am doing homework," Chelsea said. "Ghost homework. But just think about it. All the portal doors are purple, the buildings have purple auras, and even the River of Revulsion spews purple when it's angry. At least, according to the pictures."
"What about it?" Tucker asked.
Chelsea shrugged. "I dunno. I just think it's cool."
Jacob threw a wadded-up paper at her. "Go back to doing school work."
"Yes, Mom," Chelsea joked.