![](https://pbs.twimg.com/media/GGqZMQCXsAA9mYP.png)
Seen a few people attribute it to Zoro having special superior Haki but is that really the case when no top tier has it including Luffy who is clearly better in that regard.
Oden lacked these green puffs of smoke yet he is on Kaido’s list and still considered a relevant monster no one can surpass in Kaido’s eyes.
I think it’s just a visual design choice to differentiate Zoro a bit and make him look cool. I doubt it will ever be focused on or explained officially just like Asura but any good guesses?