Oh man...I like your version of my scene way better. Isn't that rather pathetic? xD Well, you're right, the dialog makes the history easier to see.
I was aiming for a few different symbols just then.
1. The change between past and present in general, youth slipping away. the poem by Wordsworth, about a rainbow, called "My Heart Leaps Up When I Behold" talks of innocence, and love of nature. Going off of that, I thought it would mean something for this girl to change her opinions about life and what she loves just for her hatred of someone and something.
2. The constantness of nature. rainbows were there as a child, and they are there now. It is not the world that changes, or nature, but us, that change. And when we change, we see things differently, and in effect, that makes us believe they change. It's about how quickly we stop caring, and about how nothing but ourselves are manipulated.
3. The main one, forgiveness. Noah and the Ark, when G-d sent down a rainbow, he made it a sign to say he forgave the world and would never try to wipe them out again. So, the rainbow is a symbol for forgiveneness and friendship. As G refuses the rainbow, she refuses to forgive O, and unlike G-d, makes no promises.
There are others, probably hundreds since everyone thinks symbols are different--that's why they're symbols. I suggest reading "How to Read Literature Like a Professor," honestly, it gave me great insight into this type of thing, and taught me how to write a heck of a lot better. I suggest every aspiring writer reads it, actually. It's very good.
If you do ever get around to reading the classics, which you totally should, since they're the best, I think do one Austin book, to get it out of the way, both Orwell books, either Dracula or Jeckle and Hyde, Peter Pan, absolutely, at least five Grimm tales, The Belljar, Dickens. Anything Dickens (except Little Dorrit, which was his first book and kind of bad), no Twain, and if you're a horror person try King. If not, and if you ever find yourself with a free year or two to pitter away, read Victor Hugo. I think, my goal this year, is to read The Hunchback of Notre Dame, and I probably won't even finish in that time.