You use such wonderful, hopeful, fairytale imagery, particularly "a rainbow that pierces dark clouds of rain". Your use of alliteration and the personification of the gulping flowers made this seem slightly like a daydream, and utterly beautiful. It's certainly cheered me up.
I also think your structure was a good choice. It makes sense to use free verse here as it adds again to the dream-like feel of the poem. I have a tendency to read poems aloud before I review them, and this read like a stream of consciousness. It was nice to read something relaxing and completely pleasant.
Personally, I think this is probably one of your better poems. I love the sense of optimism in this poem, and you've clearly got a talent for description. I know this isn't really helpful, but it's my opinion, so there you go.

I love how this poem describes a certain moment, with the rainbow, the painter, and the bird. It's like a photograph, if you know what I mean - it's a perfect recording of a moment, only in words instead of a picture. I'm almost there, sitting next to the artist myself.

The only thing I'd, maybe, change is that sometimes, you're being a bit too descriptive in the poem. Poetry is all about saying as much as possible with as little words as possible, and the many words make it feel like a one-shot sometimes. Other than that, great job :)

Ok, so this is more or less how poetry is done. I don't write poetry often, nor do I read it. I don't know why I don't read it, the few times I do I always enjoy it.

This made me really happy. Especially the imagery of the flowers drinking the rain, it seemed soothing in a sense.

Not a poetry person, but I think these lines coulda been broken into stanzas to give more texture? As it is, it's a little intimidating and brick-shaped.

"There goes a dove soaring away on sky-spanned wings" to "A dove soars away on sky-spanned wings"? Here I go about verbs again.

This has good imagery. I like the piercing the dark clouds part. That was especially good.

This is really good. You tell a fantasy that shows that beauty lies everywhere, even if it's as simple as a rainbow.