Quote 1
"Oh!" He gave a gasp and was silent, gaping. He had seen, for the first time in his life, the face of a girl whose cheeks were not the colour of chocolate or dogskin, whose hair was auburn and permanently waved, and whose expression (amazing novelty!) was one of benevolent interest. Lenina was smiling at him; such a nice-looking boy, she was thinking, and a really beautiful body. The blood rushed up into the young man's face; he dropped his eyes, raised them again for a moment only to find her still smiling at him, and was so much overcome that he had to turn away and pretend to be looking very hard at something on the other side of the square. (7.46)
So here's some insight into the otherwise difficult question of why someone with John's depth and principles would ever want someone as vapid (dull or flat) as Lenina. In a world where he has been forever different, she is someone who looks like him—that is, white and blue-eyed. John's immediate thought is companionship (check out his "Character Analysis" for more).
Quote 2
A moment later he was inside the room. He opened the green suit-case; and all at once he was breathing Lenina's perfume, filling his lungs with her essential being. His heart beat wildly; for a moment he was almost faint. Then, bending over the precious box, he touched, he lifted into the light, he examined. The zippers on Lenina's spare pair of viscose velveteen shorts were at first a puzzle, then solved, a delight. Zip, and then zip; zip, and then zip; he was enchanted. Her green slippers were the most beautiful things he had ever seen. He unfolded a pair of zippicamiknicks, blushed, put them hastily away again; but kissed a perfumed acetate handkerchief and wound a scarf round his neck. Opening a box, he spilt a cloud of scented powder. His hands were floury with the stuff. He wiped them on his chest, on his shoulders, on his bare arms. Delicious perfume! He shut his eyes; he rubbed his cheek against his own powdered arm. Touch of smooth skin against his face, scent in his nostrils of musky dust—her real presence. "Lenina," he whispered. "Lenina!" (9.25)
Compare this passage to the one in Chapter 13, when John refuses to have sex with Lenina and she ends up locking herself in the bathroom. These zippers come up again, and we get the same repetition of the words "Zip! Zip!" It's just that, by then, John is disgusted rather than fascinated—much the way his reaction to the new world changes.
Quote 3
"It was base," he said indignantly, "it was ignoble." (11.105)
John's opinion on the feely is so confusing and painful for Lenina to hear because, in fact, it is a reflection of his opinion of her—or at least of her sexual escapades.