While Broly is one of the most famous Saiyans in Trunks.

Broly was introduced in the film Dragon Ball Z: Broly - The Legendary Super Saiyan. He then appeared in two subsequent films, and a reboot movie, Dragon Ball Super: Broly. While Broly’s first few appearances weren’t officially canon within the wider Dragon Ball universe, the Dragon Ball Super film is canon, meaning Broly does officially exist alongside Goku, Vegeta, and the other Z Fighters. Broly is what’s known as a Legendary Super Saiyan, which is a Saiyan who is inherently more powerful than all others even without any training. It is said that a Legendary Super Saiyan comes into existence every thousand years, making this type of Saiyan extremely rare–though not, it seems, as rare as Trunks.

Trunks' Hair Color Makes Him the Rarest Saiyan of All

In Dragon Ball chapter 333 by Akira Toriyama, Trunks has arrived in the past from his alternate future with a warning about the impending threat of the Androids. The person Trunks really wanted to speak with was Goku, but he was still training on Yardrat at that time and wouldn’t be back on Earth for another three hours. So, Trunks spends some time talking to the other Z Fighters, who were still trying to figure out exactly who he was–especially Vegeta. Vegeta hated the fact that some random person who just showed up is already more powerful than he is (as shown when Trunks killed Frieza like it was nothing). Not only that, but Trunks is claiming to be a Saiyan, yet Vegeta refuses to believe it despite having already seen him go Super Saiyan. Surprisingly, the thing he holds onto the most to prove his point is Trunks’ hair color.

As Vegeta notes in this chapter, every Saiyan in existence, even Broly, has black hair, but Trunks seems to have blue (or purple) hair. While something like Trunks’ hair color seems insignificant, the fact that all Saiyans have black hair actually rings true even across the multiverse, which really shines a light on how truly odd Trunks’ hair color is, even with Bulma as his mother. Literally every Saiyan has black hair in their base form, including other half-Saiyans like Gohan and Goten. Even when looking at the Saiyans from Dragon Ball Super's Universe 6 (as opposed to the prime Dragon Ball timeline of Universe 7), fans see alternate versions of the Saiyan race, all with black hair. This indicates that Trunks is truly the greatest anomaly in the history of the Saiyan culture–more so, even, than the Legendary Super Saiyan.

In Dragon Ball lore, Legendary Super Saiyans occur every thousand years, and Dragon Ball Super proved that multiple universes have Legendary Super Saiyans throughout the multiverse. In fact, there are currently two Legendary Super Saiyans in the current continuity of Dragon Ball Super. However, as Vegeta pointed out, there haven’t been any known cases of a Saiyan born with a differently colored head of hair than black–making Trunks, not Broly, the rarest Saiyan in Dragon Ball.