As the jinchūriki of the Six-Tailed Slug, Rokubi can use the Six-Tails Chakra to increase his strength and coat himself for defense and protection. This is possible as the slug implanted itself within Rokubi's subconscious via telepathy and was considered sealed with Yang Chakra. It is unknown what the slug's plans are or why it wanted to seal itself within Rokubi, but with each coat can different traits and strengths appear.
Initial Jinchūriki Form
This tailless form of the Six-Tails is simply done by tampering with the Six-Tails Chakra. In this form, Rokubi's pupils become a slit and, depending on whether he has Life sealed within him or not, his eyes can turn bright blue. He also grows more animal traits such as sharp claws, larger canine teeth, and how he stands on all fours. Any wounds or injuries can be healed almost instantly by the Chakra given. This form is usually triggered when Rokubi is encountered with something personal and reminiscent, which is rare.
The first time this form was used was on the teenagers that brought him to the statue in the first place, where the slug mentally sealed itself with Rokubi. It was also used on his younger, half-brother Meimeinou after being antagonized by him, but this was a natural act of resistance by the slug.
Unlike Naruto, though, his speed doesn't increase very much. This could be because of his Bijū being a slug, but this is unverified.
It seems that this is also done by triggering an emotional side of Rokubi. Oddly enough, Rokubi can alternate from tailed forms to an initial, tailless form. He still acquires the same characteristics (sharp claws, larger canine teeth, etc.) as the initial form. Healing properties are still apart of the form, as well.
This was activated by Chinhonō continuing to tell him how he had grown and how he knew about his childhood.
Like the initial form, his speed is not enhanced like Naruto in his jinchūriki forms. Although not shown in the story, Rokubi is able to make his tails spiral at an extreme speed like a drill.
Whilst in his Version 1 coat of the Three-Tailed Form, Rokubi's irises become light blue as the slit becomes skinnier, almost a line, as his canine teeth grow even larger and two horn-like structures appear on the head of the shroud. The coat also becomes more protective and hard to destroy, and, not only is the coat bubbly, but also very slimy, possibly being a trait of the Six-Tailed Slug. In this form, he has shown to use Six-Tails Piercing Roar to throw both Naruto and Chinhonō into a nearby building. Amazingly enough, the roar was so powerful it wore away a whole, mature Susano'o. After seeing Iwayajū die, he had returned from his Version 2 coat to his 1st to ready his new, regnant form of Womekuhouou by mixing the Six-Tails Chakra with it, resulting in the enlargement of the orb.
In the Version 2 coat of the Three-Tailed Form, Rokubi looks similar to Naruto while in his Four-Tailed Transformation, completely covered in a black mask of Chakra along with an aura of light blue and white, glowing eyes and mouth. Although only seen with Life's characteristics, it has shown to be very compelling, the Chakra itself was enough to break through Naruto's Tsukuyomi.