This one is kinda AU, everything's the same, but some of the characters fire color will change and that will have meaning. There will also probably be inaccuracies about chi, firebending and emotions, but bear with me. Also, I have it so Zuko never did any firebending around the gang, so imagine he used a different weapon:swords, scythe, arrows, anything.

Zuko's POV

I'm not sure how much this group knows about fire, but I amuse myself by sitting in their circle and listening to all their inaccuracies. I know Toph enjoys it just as much as me, since we sit beside each other and I can hear her chuckling, along with the knowledge she can feel and on ocassion hear my soft chuckles. She is also aware I am a FIREbender, so I'm going to know the most on fire. However, I don't think any of the others truly care about the nature of fire, or even anything more than how to learn it, dodge it or destroy it, so I never speak up.

"Zuko, what do you think?"

I look up in surprise, this is the 4th night they've had this discussion about fire, but it's the first honest time anyone had asked me a question. I smile wryly, realizing this is more than likely because of how simple the answer was. The simpler the answer, the harder it is to see.

"Well, it depends on what you want to know."

"I want to know why some firebenders have different colors than others. I've seen a few firebenders fight us with grey or white. What does that mean?"

"It depends on color. Grey means ashamed, white means against the cause they are fighting for. The color of the fire tells you almost more about the bender than the person themselves can tell you. The fire stays one color, until the person is balanced and making the decisions they want to be. The grey will probably become a beautiful silver when the war is over and the white will become a purple color. Silver means satisfied, while purple means making amends."

"Ok.... then what about the ones with red fire? What do those mean?"

"Red is for drive. The red fire means they are completely in the right and know they are doing the right thing, at least in their mind. If you haven't noticed, Ozai's fire is red, but he's not right at all. Azula's blue is overconfidence. She thinks she can beat anyone and her fire reflects that. However, that also brings into light, the fact the color of the fire brings out some of the Bender's weaknesses. Azula can easily be angered or pushed into overconfidence enough that someone can easily overtake her with smart thinking and a clear head. Grey? Just throw some questions about how their loyalty always seems to be wavering, betraying one thing after another, and they will completely collapse. It depends only on the color of the fire."

"Zuko..... I noticed you never firebent at us. You always used arrows or swords or anything else, but you never bent at us or around us. Hell, I still haven't seen you bend, and you're teaching me firebending."

I nod slowly, figuring this would come up eventually. I smile, even as they all throw a suspicious glare my way. I figured this might make them question me. But, I couldn't have them know I was pretending to chase the avatar from the beginning. I never wanted him. I just wanted to join him so I could help end the war, but my father was too deep into my business to allow me to do that. Now that he knows what I'm doing, I don't have to hide it anymore. I forgot that, because I trained myself not to rely on my bending. 

"I'm aware of this, yes. It's something I trained myself to do. Not rely on my bending. With the color of my flame, it would've given away my plans right from the start. Uncle was the only one to ever know the color of my fire, and it's the same color today as it was back then. The color of my fire is rare and never seen, so I couldn't let it be about, or Ozai would've tried to get me back immediately, or he would've had me killed sooner. It depends on how he was feeling that day."

Toph seems annoyed by all the slow moving, and opens her mouth, but Teo gets there first. 

"So, what is your Uncle's fire like?"

"His fire is the gentlest Cadet blue color you would ever find. It's always warm, never burning you, but giving you something to follow and lean against when needed. However, mess with his family and the fire becomes dangerous, daring you to try again. I would know. I lived with him for three years and his fire kept us warm so often. I was very rarely allowed to start the fire, since we were trying to keep the color of my flames a secret."

"Ok. Then, what was your mother's like?"

"My mom was actually a non-bender, which is why Ozai panicked and tried to throw me off the wall when he didn't immediately see the spark in my eyes meaning a firebender. He didn't want a non-bending sin, so he decided to kill me. He was momentarily "happy" when I turned out to be a firebender,  but was immediately back to ignoring me, when I proved to lack anymore kind of skill or talent for it. However, back to the point, my mom was a non-bender. So, she didn't have a fire."

"Ahh.... ok. Now before anyone else asks anything,what about your fire? What is your fire?"

I smile, knowing Toph had been impatiently trying to get that answer for the last couple of minutes. I decide it's the perfect time to tease her and drag it out.

"Well.... I could tell you, but where's the fun it that? Maybe I'll show it to you instead. Or change the color of the current fire."

"Don't you dare, Sunshine. I will find out what color your fire is, even if I have to torture you somehow to do so. What color is your fire and what does it stand for?"

I decide I don't want to know her torture techniques and simply open a hand,summoning a small flame to my palm.

"My fire is black, meaning humble and honest. My father knew what my mother's moral were,  even knew she imparted all of them to me. He also knows how much I took after mother, so he knew I was bound to change color eventually. However, to get him off my trail, I started failing firebending, meaning he spent less time with me, so Uncle was the one who trained me. My fire represents me, and my morals. I never wanted the avatar, not for myself. I wanted to join you from the beginning, but my father sent a general to check on me regularly, and was known to show up at random times, just to check on me. I couldn't give it away, so I took the path I didn't want and guided you along as best I could. However, not everything went to plan."

"What went wrong?"

"You're bison was never supposed to be captured. I almost gave away my secret to save him, but managed to finally cut the chains enough for him to escape. The girls weren't supposed to be caught by Combustion man, and I hadn't planned for Katara to be down in the combs with me, so I had to improvise. However, things went pretty well, everything considered. Now, I'm going to go to bed, since it's late and we have early training tomorrow, and I might show you some actual fire, if you're on time. All of you are welcome to watch, if you wish,but remember it all depends on if Aang is on time to training."

I leave and head to my room, stripping to my pants and then covering myself with a blanket, getting on the bed and thanking Agni I'm a firebender, as my bed heats up and keeps me at the right temperature. I wake early and head for the courtyard I've been using for training, smiling when I hear the shuffling of several curious people. I'm not surprised all of them are there, sitting on the sidelines, except Aang, who has 10 minutes to get up and ready. I sit down and start to meditate, loosing myself quickly, knowing I need to be able to control the fire I've been suppressing for the last couple of years. It was very painful and it still is, but I manage.

"Finally here, hmm? Looks like you're in luck, there was still a minute on the timer. I'll be using flames today."

Aang smiles brightly and nods, before settling into his normal warmups, and I let him, but stop him before breathing.

"You are mostly going to be trying to control your flames, not their size or shape, but it, so you will be doing plenty of breathing later. For now, let's just get your forms and stances corrected. Ok?"

He nods and settles into the basic one, while I make small adjustments. We continue like that until he knows the correct way for each stance.

"Ok, I'm going to give you a demonstration, and then you must do your best to copy it to your capabilities. Got it?"

He nods and steps back slightly, letting me have some space. I slide my front foot forward and drag it along the ground, sending out a wave of fire, before I quickly slam a hand into the middle of the fire circle, and spin a few times, weaving my legs to create a spider looking thing, before resettling on the ground.

"That was awesome! Your fire moved gracefully, and then it maintained form even when you weren't directly in contact with it. Nice."

"I don't know how you did it.... but I was able to see you're fire...... and that was awesome. I don't even know how to describe it. Maybe you could show the others how to do it? It'd be nice to see how water and even wind work, maybe steal some moves from them once I understand what it does."

"I can teach them, if they are willing to learn. But, first let us finish the lesson on firebending, yes?"

"Of course. I'm just going to enjoy the show."

I settle in and the training session continues like this, me demonstrating and him attempting, before I gently correct him until he's got a simpler version of it down, before moving on. As noon comes, I decide this is as good a time as any, and motion Katara, and Haru over as well.

"You are all benders. But, Toph can't see without vibration, correct? Now, I want you to hum while you're bending. Try and just hum while bending first. Once you get that down, I'll tell the next part. But let's eat first, ok?"

"That fire, it was so beautiful. I can see now why you hid it though, it's really easy to spot. Do you think I'll ever be able to tell the difference between all the colors of fire?"

"It'll take time, but yes, you can. All of you can. You don't have to be a bender to see color, you just have to know what you're looking for and understand what it's represening, and thus what it's  weakness would be. Keep in mind, the tricks do not always work on the bender. Most are aware the color of their fire is important and know they need to cover their weakness. But most couldn't care less or just aren't very good at hiding it."

"Ok. But, didn't it hurt you to suppress your bending the way you did?"

"A lot, and I still feel sore even now, probably from my chi paths finally being used, because I haven't used them in nearly 3 years, so they're sore. I tend to be a bit useless when I suppress the urge though, because the pain has become instantaneous and tends to drop me where I stand. I've barely managed to drop in my room several times, since coming here. It hurts more to do so, but I needn't ask for help, when I've been doing this for years."

"Let me see those chi paths. I might be able to help, since you do need to be able to firebender without pain in order to teach Aang. Maybe you'll be less emotional when I'm done. Sit."

I play with some fire in my palm, while she rests her glowing hands on my chest, and I soon feel the constant pain fade away. I relax almost instantly and sigh, the fire growing a bit in my palm, before I quickly snuff it, knowing it may grow more as she goes. Oh, well, growing is in fire's nature as much as spreading is. 

"Why were we even stupid enough not to ask him in the first place? He's a FIREbender. We waited 4 days to ask the only person who probably knows most, simply because he was sitting right in front of us, laughing with Toph. Do you realize how stupid we had to sound to him, and how much he probably laughed at all our inaccucuracies."

"To be fair Sokka, you would probably do the exact same thing, if not before telling them exactly what you're doing, he was just more subtle about it. Flaring the fire, growing the fire, shrinking and dulling the fire. Subtle. Clumsy. Subtle. Clumsy."

We all laugh at poor Sokka, though he knows we jest and he knows he'd do it,too.