Since this new power was introduced the community has been confused about whether some attacks carry ACoC or not.
At the same time, Oda has made no effort to differentiate the different types of haki in the drawing.
The only way to solve this is for haki users to always use the strongest type of haki they have, whether CoA, ACoA or ACoC.
So I think Oda simply doesn't draw those three types of haki differently because he assumes that whenever haki is used the latest version is used.
So, when we see black rays or black limbs the user is using their most powerful haki.
Issue solved.
At the same time, Oda has made no effort to differentiate the different types of haki in the drawing.
The only way to solve this is for haki users to always use the strongest type of haki they have, whether CoA, ACoA or ACoC.
So I think Oda simply doesn't draw those three types of haki differently because he assumes that whenever haki is used the latest version is used.
So, when we see black rays or black limbs the user is using their most powerful haki.
Issue solved.