Bringing Out the Blue is a Avatar the Last Airbender AU fanfic by maguena1. The basic idea is that when Zuko saves Aang as the Blue Spirit, instead of being hit in the face and knocked out, the arrow goes into his shoulder instead. Because of this Aang doesn't learn who he is, and helps him heal from the injury. Zuko sees this as an opportunity to infiltrate the Avatar's group and learn where they'll be next, so he can ambush them later. However, he finds himself becoming their friends, and really liking them. This change affects the whole timeline, mostly in minor ways, but the farther down the Rabbit Hole you go, the bigger the gap is.
On the negative it seems at times like the author's prejudice against certain characters is shown instead of the actual character, the example that comes to mind being that of Jeong-Jeong, who every character makes fun of and is the butt of many snide comments. While it isn't really a problem for me, some people might find his look into the main character's heads completely out of character from how they would think. Personally I didn't think that once, but I can see how it can easily bother others.
Now for the good, and boy is there a lot. The dialogue is really good, and feels like something out of the show. The way the "new" character of Blue interacts with the Gaang is very good, and makes a lot of sense. The looks into many of the character's heads are very interesting, and some of the Fanon here is quite good. Easily my favorite part, however, is his/her handling of Zuko. Before this fic Zuko was a good character for me, very well written, but he was never my favorite. Hell, he never breached the Top 3. This fic really changes that. The way he/she shows Zuko's thought process, mindset, and general sense of self is fantastic to me, mostly because I can relate in some ways. If anything, the Zuko of this fic reminds me of a dark version of myself in some ways, a me raised under very different conditions.
Overall, this is a great fic, and I have added it to the small list of ongoing fics that I check up on every day to see if they've updated. If you like Avatar the Last Airbender at all, I would highly recommend this fic, even if you're not much into reading Fan Fiction. Laters.