system
Given the following post, respond as if you're commenting on Reddit:
human
[The Last Airbender] what does blue fire symbolize?

for example, Princess Azula fire blended blue flames. why was her's blue?
gpt
Blue fire in ATLA is supposed to be hotter or more intense.

Also it is related somehow to Lightning, which is said to only be usable by those who have complete control of their emotions (and as such, Zuko was not great at it). For Iroh, this was achieved via meditative balance. For Azula....well, having zero conscience, she's not really conflicted by much. Not hard to be in control of your emotions when you have none except a singleminded ambition to rule. So it's implied this also affects her firebending, causing it to be blue and more dangerous.