That doesn't prove anything.. You're saying it's what mattered, not Oda.. He always never give all the informations and readers have to extrapolate..
It's all sorts of colors, but when characters get serious and not using perfected AdCoC, it's Black with a unique color..
Then why isn't it Black here..
The Haki lightning is Black, the Haki blast attack isn't..
It's all sorts of colors, but when characters get serious and not using perfected AdCoC, it's Black with a unique color..
Then why isn't it Black here..

The Haki lightning is Black, the Haki blast attack isn't..
Ok look that panel in white in black is easily described. The blast = Air Bar Slash the same one Zoro/Shanks/Mihawk/Any Swordsman uses to send slashes but in this case its a blunt slash like Kaido and other characters who don't use swords. And they have always been in white in manga.
And before you say anything. Even Zoro did blunt slashes if they didn't want to cut whos in front of them.
Now don't distract from the main discussion here and go on a rant on air bar slashes. We are only speaking about haki is black and Oda's words that divine departure and oden's attack are CoC attack.