Haki sparks comes in different colors and can vary also from the user state of mind..
lt can be Blue as with the Don Chinjao Luffy clash on chapter 716..
lt can be Purple as shown with kaido chapter 923..
As well as many others, Yellow, Dark yellow, Dark red, Teal, Black and Red alone being the only
instance where Advanced CoC is used..
The visible Haki dispersed in a CoC clash is CoA through invisible waves of base CoC and here is a good
analogy to understand the concept with Jinbei's secret fishman karate technique..
ln both events CoA lightning is diffused through another medium, in the Jinbei fight its
running parallel to fishman karate waves and in Dressrosa its running through conqueror
haki waves which are invisible in each images..
Then there is the matter of color variation.. For this reason that Roger's attack on Oden was
first depicted as Yellow in the Vivre Cards and later in the Colored Manga as Dark Red energy
blast..
An identical result can be observed in Luffy vs katakuri..
The initial passive display of power is Yellow CoA
Then when Luffy is overwhelmed and has to rely on his will alone the haki clash of the
same blow turn in a dark red CoA lightning.. Going from passive to agressive..
So all Haki color sparks have been CoA aside a single one pure red used by Advanced conqueror haki
users.. Such as Roger vs Whitebeard..
One difference between CoA lightning and CoC lightning (other than not touching) is the vector,
Visual CoA haki is diverging as an excess of energy where as visual CoC haki is converging to the users
will..
These principles apply to high grade swords and swordsmen with aerial charged up haki slash too..
Per shown with Roger's kamusari CoA imbued colored beam.. Those sword techniques may or
may not require base invisible CoC for activation of a superior haki power generated blast..
For instance Zoro needed to unleash CoC to use Enma at its full potential..
Which can also be seen in the vectorless or motionless Haki lightning while being
in that awakened state.. The Haki sparks are neither converging or diverging but simply hanging around
the blades.. Along with the green smokes..
Plus the additional confirmation of the haki lightning being black from the cover volume.. As mentioned before
all colored haki sparks being CoA with or without base CoC conjunction..