Yes, it's a long page of Lenalee's total look. We'll talk about her hair, clothes, and even eyes. Yay?
If you're new to this series or do not know of it at all, you might wonder why you see images of Lenalee with different hairstyles. Sometimes it is long, on the other times it is extremely short. I'll give you a brief explanation: Lenalee's hair was pretty, long and black, but on later chapters it got burnt and turned out extremely short. On the most recent chapters, it has slowly... or even quickly, growing out again.
Chapter 5 - 72. Lenalee's hair is usually done in pigtails. It seems that Lenalee's hairstyle has been decided even before D.Gray-man starts. Her prototype (in Zone) who goes with the same name, has long hair with as well. Zone!Lenalee, however, has her bangs tied along, unlike dgm!Lenalee. But they look identical when their hair is undone.
Her hairbands might be something small and black, because we never get to see them. In chapter 64, Anita lends Lenalee a pair of hairbands inherited from her late mother. Because they're precious, Lenalee has her eyes on them even in her full invocation. She is able to save one of them, which Anita uses for the first and the last time.
Special: Chapter 22-26. Road dresses Lenalee up. Her hair is still in pigtails, but with curls. Very elegant.
Chapter 74 - 156. Lenalee's hair is burnt due to the air friction caused by her attack upon Eshi. Actually, her body is also burnt, but the Innocence saves her immediately and Miranda uses her Innocence to recover her wounds and her ripped clothes. However, her hair isn't restored to how it was before. I find it strange, honestly. Since the wounds on her skin are part of her body, then her hair should be able to restore its length as well. As for the legs, I think it is more logical because Lenalee's Innocence is the one affecting them. It is very likely that Hoshino-sensei just wants to give her a different look. Some fans prefer the long hair to this, but some other likes the new hairstyle better because it makes her look a little "badass".
If we look at Lenalee's state after defeating the Level 3, she is very weak and dependant to others. She can't do anything but protected by the others, which gets the fandom to name her "the damsel in distress". If her hair was still all long and pretty, the title will stick to her even more... because of the image of a princess. Yeah. Maybe I'm thinking too much. Other than that, the cropped hair also gives a different touch on her reunion with Komui after the team returns to the headquarters.
Chapter 157 - 164. Lenalee's hair has started to grow. I don't have much to comment, so yeah. :D
Chapter 165 - present. Lenalee's hair has grown some more! I really like her in this style. Somehow she resembles Naoto from Dogs by Shirow Miwa, but that's fine.
Lenalee's eyes are normal—as in not cursed like Allen's. They are easier to describe or draw, but I always have a hard time when I colour a fanart or a manga shot of her. In some official manga pictures, Lenalee has brown eyes. In more recent pictures, they are purple. Anime screencaptures show purple-eyed Lenalee, but in some anime artworks they are brown. And in D.Gray-man trading cards, they are green. What now?
Lenalee is an Asian, so theoretically her eyes should be brown. But yeah, this is an anime/manga. We can't really ask for something factual.
So I guess we'll believe in either or , because Bak Chan said so in the first volume of D.Gray-man novel. If you know how much of a stalker he is, I guess this information is trustworthy. :)
Lenalee's appearance in Zone really affects her looks in D.Gray-man. . Heck, zone!Lenalee even has miniskirt for her wedding dress! But it isn't her choice since the Earl's minions choose it and dress her up. I guess Hoshino is determined to design a hot, pretty female character with hotpants and miniskirts. (Afterall, Lenalee was modeled after her ideal person.)
In one of the omake pages of DGray volume 5, a fan asked: "Does Lenalee wear anything under her skirt, but over her underwear?" Reever, who was in charge of replying the questions, didn't answer it because he was frightened of what Komui would do to him. However, this mystery is revealed in the inner cover of the fanbook.
Lavi: You wear shorts under the skirt??
Lenalee: Yup. See. *open*
Allen: *blush* Hey, Lenalee, you shouldn't!!
We can sort of see how innocent Lenalee is in this picture. XD But actually, the inner covers are sort of like... an omake, so you cannot take it really seriously. I think Hoshino drew this cover in order to answer the unreplied question.
Further opinion regarding the whole mini fashion can be found here.