I think I’ve actually done it. After over 15 years, I think I may have actually discovered the reason behind Azula’s blue fire, as well as the reason dragons are able to bend multiple colors, and Zuko’s, in the comic.

Many ideas have been presented to explain Azula’s usage of blue flame, but the most common explanations tend to agree it has something to do with either her prodigious skill, or her sociopathic nature. I believe that it is at once both of those things, and also neither. Before I can continue, let’s discuss the broader concept of firebending, and by extension, bending in general.

What is fire bending?

Putting aside discussions of genetic inheritance, the broad definition of fire bending is one’s ability to control and produce flame, combining martial arts, and spiritual energy, or in the Avatar universe, their chi.

Chi is used by all benders, but none more so than fire benders, who directly expel their chi to produce the element they bend, something that other benders seemingly do not have the ability to do. As explained by Iroh, fire bending comes from the breath, but it is more complicated than that.

In season 2 episode 18, a character by the name of Guru Pathik informs Aang that the body is comprised of seven distinct chakras from the base of the spine to the top of the head. Four of these chakras are associated with elements, three not. For now, let’s focus on fire. The fire chakra is, as you’ve probably guessed, located near the stomach at the Solar Plexus, the area that controls breathing, and in Avatar, fire bending. Why is this important?

Chakras are pools of swirling energy, or, as we’ve already established, chi. The fire chakra produces fire chi. Benders use fire chi to bend fire. What color is the fire that they traditionally bend? If you said orange or red, I wouldn’t fault you, but you are incorrect. The fire that they bend is yellow. It is tinged with orange, and sometimes red as well, but the primary color remains yellow.

Something I have neglected to mention thus far is that the seven chakras are associated with the seven primary colors; red, orange, yellow, green, blue, indigo, violet. Each chakra is associated with one color, and what chakra is associated with yellow? The fire chakra.

I’m sure you’ve guessed my theory at this point, the color of fire one bends is associated with the color of the chakra they pull their chi from. I also believe that due to the proximity of the water chakra to the fire chakra, most fire benders also pull from there as well, which causes their yellow flame to be tinged with orange.

How does this relate to Azula? The location of the blue chakra is the throat chakra, also known as the truth chakra. I believe that Azula can channel her throat chakra and her truth chi to produce blue flames. How, and why? I believe that this is where her natural talent and personality come into play. The throat is another part of the body associated with breath, providing a connection to her fire bending, and I believe who she is essentially tore the throat chakra wide open, providing her with a vast amount of chi to use in her fire bending.

As for why? I don’t personally believe that her fire burns hotter than other fire. I’m aware that in our world, blue fire is hotter, but I believe that in Avatar, the color of fire is more to do with where one draws it from, and that heat and power come down to one’s skill. So I believe that SHE is more powerful than most and that SHE can make her fire burn hotter than most, but I do not think that her fire burns blue because of her power, so I believe she chooses to bend blue flames for a handful of other reasons. Primarily, I think she chooses to do so because of the prestige. She is uniquely able to bend blue flame, and that makes her special. She likes being special. Azula also likes being feared, and having a unique flame makes her terrifying.

If you’re still wondering what truth has to do with her character, I say everything. To qualify, I believe that there is a difference between truth and fact. Facts are objective and ineffable, but one can be wrong and still tell the truth as they see it. She may lie, but when she does, she makes the lie her truth. She believed her mother thought she was a monster (S3 EP 5) and she believed that she was, and had no reason to contradict that thought.

If that wasn’t enough to convince you, my final argument on the matter is in season 3 episode 10, where she was able to manipulate her truth so well, she could convincingly lie to Toph, who could tell when someone was lying, that she was a “400 foot tall purple platypus bear with pink horns and silver wings”. In season 2 episode 16, we find out that Toph cannot tell a lie if the person telling it believes that the lie is the truth.

Enough time with Azula. If we follow my logic, it doesn’t take much convincing to believe that the original fire benders, the dragons, could alternate which chakra they pulled from, either as an emotional expression, or simply as a flex. I believe that Zuko’s usage of multicolored flames is similar. In a moment of desperation, he pulled more chi from his system than he ever had, and that pulled chi from other chakras, resulting in his awesome display.

Anyway, that’s all I have today, I hope you found my theory interesting, even if you don’t believe it yourself.

Edit: I scoured the internet to see if this had been theorized before, and to my knowledge it hasn't. If it has, well here's a useless post

Edit 2: link to u/Pretty_Food comment on the thematic and practical design choice for the blue flame. It's great info, and I corroborated it by looking into the book myself.

Ultimately, though, to restate a reply to a comment earlier, there's two frames of thought in regards to non explicit canon that boil down to why the author did it, and why the story makes sense with it in the story. u/Pretty_Food has an awesome explanation to the former, but the latter still merits considering. If the canon explanation is that she's simply more powerful, why do her feats not scale to be above Jeong Jeong, Iroh, Ozai, and any given Avatar? If it's simply about power level, every avatar should have blue fire. My post is an attempt to explain the lore behind her skill, not deny it.