“Blue fire: Only Azula has demonstrated blue firebending. While not to be confused with lightning, blue fire also seems to possess more physical force and produces a combustive effect that is more intense than that of normal fire.” -Avatar Wiki
This explains why Azula's able to cut clean through solid objects. This move is called "fire blade" too -- and it's sharp.
Red fire:
Blue fire:
Blue Fire is a cutter, more focused, cleaner; burns the oxygen more effectively than (dirty) red fire.
This explains why Azula uses her fingers instead of fists for the most part. Even when she was younger, Azula always prefers precision over strength (ie uses her fingers and mastering her katas perfectly before firebend).
Blue fire is precise and deadly, just like Azula. It suits her perfectly.
-Sifu Kisu (the fighting instructor and consultant for the Avatar franchise)
Firebending is based on Northern Shaolin style, except Azula who gets her own sub bending style (and Toph). Her firebending is mixed of both Northern Shaolin and Chachuan, but it stands different from other firebenders due to the intentional Chachuan element.
"Unlike Northern Shaolin, where nearly every strike is delivered with a high degree of power, Chachuan’s forms and attack sequences are performed in continuous waves, with each movement leading into another, coalescing into a single (or multiple, depending on the situation) powerful strike(s) at the end. [...]
Chachuan is a style that embodies contradiction and balance, and has been heralded as vigorous, yet precise, graceful and authoritative, elegant but forceful. In combat, skilled Chachuan practitioners must be extremely efficient, due to the high physical demand the acrobatic style places on its user. The prodigious skill required of a Chachuan practitioner, along with its renowned beauty and effectiveness, make it the style perfectly suited for Azula’s personality."
Source: Fighting Styles: Azula by @kyrievali
Chachuan system suits Blue Fire, and of course, this created the ultimate fighting style for Azula. Different and strong.
Me, making this post:
To add further to this great post:
The only times we see Azula use a fist instead of just her fingers are when she fights Zuko at the Western Air Temple
and in their Agni Kai
Azula only chooses strength over precision/only uses more typical firebending moves when her mental state is deteriorating, and both times she acts like this the fight ends in either a draw or what would have been an earlier defeat had it not been for the lightning at Katara.
Avatar, lliterally proving once more, to be one of the best western cartoons to have ever been produced.
