[quote=@Gisk]
White is also the hottest something can be. Azula's flames were blue because of the strength of her bending, and it was a big deal that they were that strong. Even Ozai still had orange flames. 

I don't think anyone should have white, and blue would even be pretty out there. 
[/quote]

Remember in Avatar world, it's not the color of the flame that is what makes it hot. It's the persons willpower. The colors were not just the color of the heat. It was more a spiritual connection. Azula's flames were the strongest not just because they were blue, but because of her overwhelming will that fueled it. Her power hungry drive. Remember a Firebender bends fire through their determination, their will, their inner emotions. We have seen Zuko's flames beat Azula's when he is angry because it is emotion that controls the heat. Emotion and will.