I voted on trb(adam) and bllb(blue) and nobody asked me why but I want to explain.
Okay, so, trb is obviously a set-up for Adam as a character(who he is, what are his thoughts, ideologies, feelings, etc) and bllb is him already changed from accepting the consequences of his bargain with cabeswater. I understand both takes about it but I think we have four main points to take into consideration here:
First: Blue, even though is supposed to be the main character, sje not really that explored in trb. I personally think her personally was much more flashed out in bllb than in trb
Second: The second reason is the names of the books. Now I know everybody would get to the conclusion that bllb is about blue due to the name and that, because it is so obvious, it could be wrong, but I am specifically talking abou trb's name, and not bllb's. Let's star by analyzing tdt's and trk's names. Tdt is obviously abou Ronan, we all know that, but Ronan is not the dream thieve, he is the greywaren. Some people might say that the dream thieve is kavinsky, some might say it's actually Niall(I think both takes are valid and might not be mutually exclusive, even though, due to the dreamer trilogy, I tend to see it as a whole universe and fall in the Niall side of the venn diagram, especially because then we can introduce ronan as an obvious mirror to niall), this is shown at the end of tdt, when Ronan is trying to dream something to stop kavinsky and adam is scrying to help, when cabeswater says "there are many thieves, but only one greywaren", stating Ronan as someone who ir NOT a thieve. So, the conclusion that we can get from that is that, even though the book is about Ronan, the title doesn't necessarily need to be, it is only ronan-adjecent.
Another conclusion from this is that the titles can seem to br talking about someone but actually be talking about someone/something else, which is something that happens throughout the entire series. It actually happens again in trk, where we are taught to believe that the Raven King is glendower when it is obviously gansey. It, again, could be said that they are both the raven king as gansey is an obvious mirror to glendower, but that is another thing entirely(I could write about that if any of you are interested). Again, we can draw the conclusions that the titles don't always mean what they seem to mean at first and that they can represent more that one thing/person, who is adjacent, somehow, to thr book's character in focus.
This line of thought can also be drawn on both the other titles. Blue Lily, Lily Blue also seems to obviously mean, well, blue, but no. This is something that was said by Gwenllian and by Noah, as he was being possessed by gwenllian. This was once again repeated by her when she was trying to explain blue's mirror-magic to her. Blue Lily, Lily Blue is not about Blue, it's about blue's relation to gwenllian and the way that one mirrors the other(in much more that just the powers, I ca also talk more about that later). Thus, we get to the conclusion that bllb is blue-adjacent and represents the way blue mirrors gwenllian.
This line of thought can also be applied to trb but I'm going to leave this to the next point.
Third: Adam is the TRUE main character. There, I said it. At first we are taught to believe that it's blue, than blue and gansey, than all of them, and, after reading the dreamer trilogy we think it's Ronan because everything has always been about Ronan, but it's exactly because of that that everything is actually about Adam. Okay so this is probably going to be huge and confusing BUT let's begin. Okay so we can start by that scene in trk where Maura and Mr. Gray are talking and they get into a little argument as to whether it's gansey's crew of merry man or Adam's. I am personally on Mr. Gray's side. It's Adam's crew of marry man. Now, I could get into a massive rant as to why Adam is the main character and I did plan to but i realized it's not that relevant why, only that it is, so I'm saving that up for another post.
it's been over a year since I started this but I completely forgot about it in my drafts and I actually don't remember my fourth point but I know I had one, so I guess that counts. anyway, enjoy my rambling