【How-to】Why is future trunks hair blue

Like all Saiyans, Goku has a monkey-like tail that allows him to transform into a great ape on the full moon. The Saiyans who live on planet Vegeta (Paragus, Badrock, Nappa, Vegeta, etc.) wear their tails wrapped around their waist like a belt. This keeps their tails from being reached or gripped by opponents.