How we cite our quotes: (Act.Scene.Line)
Quote #1
YORK
A day will come when York shall claim his own;
And therefore I will take the Nevils' parts
And make a show of love to proud Duke Humphrey,
And, when I spy advantage, claim the crown. (1.1.250-253)
York lets us in on his plan from the very beginning: he'll pretend to be on Gloucester's side, but he'll actually make a play for the crown himself. Regardless of whether he's justified in taking the crown, he doesn't display much loyalty to anyone. He's ready to switch sides and even double-cross someone just to get what he wants.
Quote #2
GLOUCESTER
Nay, Eleanor, then must I chide outright.
Presumptuous dame, ill-nurtured Eleanor,
Art thou not second woman in the realm
And the protector's wife, beloved of him? (1.2.41-44)
When Eleanor admits she wants to be queen, Gloucester chides his wife. He values loyalty and realizes his wife has none. His upstanding code of ethics is contrasted with the codes of others who switch loyalty all the time, as if they're playing a game (and cheating at it).
Quote #3
MARGARET
She bears a duke's revenues on her back,
And in her heart she scorns our poverty.
Shall I not live to be avenged on her? (1.3.83-85)
Margaret is on to Eleanor. She knows that Eleanor is trying to get more power and that she's not loyal to the crown. Now, Margaret's suspicious of everybody, but she's actually right this time—Eleanor does want more. But it hardly matters whether she's right or not; when Margaret's in take-down mode, it's all over. She just uses Eleanor's "disloyalty" here as an excuse for getting a tighter grasp on power.