Blue tells the story of two girls, one uncertain of her future who decided to go off a live a college life, and a social outcast who really just lives day by day as she please, who also doesn't have much of an answer about her future. By pure curiosity and common ground in this area they become friends.
Blue is good for many reason which I hold in high esteem. For one, it's unrequited love. While not trying to spoil the story Kayako will unfortunately be unable to have Endo as she wants, where as Endo plays the role as the sexually curious girl. While I haven't read a lot of Shoujo-Ai, of the mangas I did read, it appeared that the girl usually expressed similar feeling. To read this was a nice departure from that, because in real life, the one you love may not love you back the way you want them to (despite me actually saying "Oh that's bullsh*t" at the end because of the unrequited love)
Blue is also one of the few times I read a story involving a sexually curious character like Endo. It's not this first time there has been a character like Endo. Have a story about someone who just living to be living isn't new. Nor is Endo's reason anything special. But I feel like Endo understood the implications of her actions and would willing given into Kayako desires despite them both knowing it isn't the same because she loved her. Parallels could drawn to Aoi Hana in the same way. But what makes Blue different is that Endo clearly in heterosexual but at the same time comfortable experimenting with someone who she can get close too like Kayako as long as no one is hurt.
The story also does a good job with pacing and development. Endo effectively grows up and Kayako grows founder. But these processes aren't over the top or crazy. Kayako does spend even chapter crying. And while the ending will probably hurt diehard Shoujo-Ai/Yuri fans it was satisfying.
But I couldn't give Blue a 10. A big reason for why I demote this to a 7 is because I felt that not enough outside events happen to support these girls development. Endo grows up and we can assume because she settled things in her past and with people around her, but I would have liked to see these play out.
The art style of this manga is unique and I like it, but because you can't really tell the two girl a part until later in the manga, it makes following conversation between them hard. For me this confused the story a bit and I had to often re-read section more than once. This reason alone probably accounts for a demotion from 10 to 9.
Outside these reason I feel Blue is a good read and if you look past what I disliked you will enjoy it.