Broly in Dragon Ball Heroes turns into Super Saiyan 4, but before that he has a "legendary super saiyan" transformation others saiyans don't have, and also he has a red aura instead of yellow, though this could mean he's in the limit breaker Super Saiyan 4 form .
Is Broly Super Saiyan 4 a regular Super Saiyan 4 transformation or does it have something "Legendary" and different from the others Super Saiyan 4?
From Dragon Ball Wiki - Legendary Super Sayan 4
Broly's Super Saiyan 4 form is largely similar to Goku's Super Saiyan 4 form, although the main difference is his having a significantly built frame and blank eyes (similar to his Legendary Super Saiyan state). It also has a yellow aura when in use, and is one of the few Legendary variants to not have Broly possess emerald hair.
The Legendary Super Saiyan 4 form, like Legendary Super Saiyan 3 and Legendary Great Ape, is only seen in video games. Broly is shown attaining this form thanks to assistance from Black Smoke Shenron, who uses his shadows to transform Broly into a Super Saiyan 4 in the JM7 trailer for Dragon Ball Heroes, and then proceeded to fight and nearly kill Super Saiyan 4 Goku and Vegeta, and Super Saiyan 3 Beat but was struggling against Super Saiyan 2 Note before Super Pikkon arrived.
Broly Super Saiyan 4 is different from other Super Saiyan 4 transformations as it was attained through the negative energy from the Cracked Dragon Balls and Black Smoke Shenron.
The red aura is present at Super Sayan 4 Full Power which is more powerful than the Super Saiyan 4 form, seemingly a combination of the former and Legendary Super Saiyan. Broly attained this form around the Assault on the Hell Gate Saga and used it to defeat the Time Breaker leaders.
