I love the first line! It really opens the poem. (*dawn'S) I know you're trying to stick to 4 lines in each stanza, but...I don't know. You've read one of my poems and know that I love imagery. I couldn't imagine how your lover was a rainbow. Was her personality colorful, thrilling, luminous?
In general, there was no story to this, no background or given foundation. It sounded like random pretty lines tossed together. BEAUTIFUL lines and wording, but they don't make sense without the fat around them. Each line has detail, but none of that detail sheds light on anything else around it, doesn't connect everything. Keep focused.
Also, the Lady below was right about the rhyme scheme. Pick one and let the words flow. Don't push yourself. Just breathe, FEEL everything as intensely as you can that makes you love this person, and write away.
I always enjoy love poems -- as long as they aren't cliché -- so I can say that I enjoyed this, much. It's a lovely little ode.
I am one of those writers that tends to believe in improvement. I am more dogged toward my own writing, but I do have something to say about this. I am not sure how you are about critiquing, so I will say that I'm not trying to change you in any way, just offering up insight beyond feeling.
Technically, your rhyme scheme...well, there isn't a scheme. You go from xxaa to xbxb to...free verse. My suggestion would be to even this up by eliminating all rhyme. It would make for more consistent reading and the reason I don't suggest going for a set rhyme scheme is because I don't think it would do it justice. This also opens you up to more original synonyms for your rhymed words. If that makes sense.
I particularly enjoy the idea of being personified anew. Even as is, it's precious.