Were the Admirals using Busoshoku at Marineford?

[SSJ2]

Are we meant to assume that it was shown invisibly for all Haki users? There's absolutely no reason as to why they wouldn't be using it.

 

[Future Warrior]

All Haki shown Pre-TS is invisible. But to answer the question, we saw all 3 of them form outward flowing Haki to cancel out Whitebeard's attack.

 

[SSJ2]

So WB was using it but couldn't use Haoshoku?

 

[Future Warrior]

He was probably using basic Haki like armament and observation, just not as well as it could be.