Here is how I would approach this Pink Tie/breast cancer thing. Delta, (I believe is the sole sponsor of this event) and there will be no charge to those who come to this event. I think this is a great departure from the for profit job fair model.
So how would I "pay it forward"? Well since this saving me a few bucks, I would put my pink tie on, and when I walked through the front door I would ask to be directed to the donation box and toss in what I thought was appropriate.
Not because its a charity to which I'm currently giving(I'm not, I've got about 3-4 others) and not because I've got a personal connection, I do, but well it's personal and not relevant, and I certainly wouldn't expect to be questioned about it.
But because this is part of Delta's corporate social responsibility policy which is part of Delta's corporate culture. It's their "living room", they are the host and being the gracious guest that I am, I'm not going to get into any deep discussions about csr or my charity is better than yours.