Well just saw it, let's have a crack at it... First reaction is that within the first 5 minutes I think you know that this is not a movie where you're gonna get any kind of straightforward message or meaning, or maybe not get any at all. Which is fine by me. The opening image is of a paper chain covered in philosophy lying in the dirt... I think? Maybe that represents what this movie is. The first line is "close your eyes", so you get the vibe this movie is not something you're supposed to "understand". This movie is hard. It's like Legendary difficulty.
Next thing is how the movie kind of hovers around people, not just at the beginning but throughout the movie, like you'll get a small slice of someone's story before it moves on.
I haven't checked but I can guarantee that most critics would compare the way this movie is filmed to a Terrence Malick one, especially The Tree of Life. Carruth seems to have a major hard-on for nature and sort of seeing what our relationship is with it, there's a lot of controlling nature from the potted plants that the Thief uses for the parasite and the caging of the pigs, and of course the mind control used on Kris.
I think the clearest theme would probably be a "spiritual" connection between people (or animals or whatever). At the beginning you have the kids who seem to have some kind of psychic link (?), Kris and Jeff obviously have their connection (there's a lot to talk about there but honestly it's the morning after New Years and my brain is a Jackson Pollock right now), and of course there seems to be some influence the pigs/parasite things have on Kris and Jeff's lives (or vice versa?). The end shows Kris embracing a pig but honestly I'm not sure if it's a happy or a bleak ending.
Repetition seems really prominent too... you have some scenes that repeat over and over again (the starlings, "I hope today is better" etc), there's the cycle of the grub/human/pig/plant. And one of the first images of the movie is of a recycling bin, although I can't remember right now what's put into it. Is it the philosophy chain link? If so I think that's important. We're in Finnegans Wake territory here...
The Sampler (sound recording guy) is the most interesting character to me. Putting aside the parasite/human medical experiment... thing. He sort of drifts around like a ghost, just observing people, a bit like how the film does that itself. He's also recording sounds that we the audience hear, so he's sort of making the movie himself. There's also a big connection between sound he records and the lives of Kris and Jeff... but I'm not sure what. It's a really striking moment when Kris cuts one of her sewing threads and the Sampler like... loses his connection to her? Or loses interest? Or something?
I'm wondering whether Carruth is a cinephile, and maybe wondering if a lot of this movie is about how to make a movie in the first place. Like about the creative process. Kris is editing a movie, which is A Topiary, the film Carruth had begun before deciding to make Upstream Colour instead (thanks IMDB!). The Sampler is like someone who sort of just looks at people, I feel like he's sort of like (and here's where I really start going off on a tangent) representative of the audience or maybe the filmmaker. He just observes all these stories, and at the end it's like Kris and Jeff become aware of his presence (and then murder him), like it's Carruth saying this is not a movie that you just observe without thinking about it, like he's "killing" the usual kind of audience expectations or film-making conventions.
Yeah, it's flimsy, but Jesus what do you want? I'm not Quentin Tarantino. And I'm hungover. Double whammy. I do feel there is a lot of stuff that sort of points towards Carruth examining the process of creating a story. I don't think the movie gives any answers, just wants to make you think, which is how I think is a good way to operate.
Some other stuff, like colour is important (no duh, clue is in the title), like blue and especially yellow but I've written a lot already. Also don't think you can ignore the way the story has a lot about financial fraud, housing equity, bankruptcy, poverty, wealth, unemployment etc. Honestly you could talk all day about this movie, there's so much I'm leaving out.
One more thing, and that's how cleverly Carruth marketed and distributed the movie. Tiny budget, no stars, limited theatre release. But online distribution and great use of word of mouth have helped. He's really been successful in promoting himself as a trailblazing indie hero. And I hate to finish on a cyncical note... but I wonder if he purposely makes his movies so strange partly so the movie will generate buzz and discussion as a means of promoting the movie.
Kind of like how I just spent half an hour writing this post... Damn you Carruth! No, that's being unfair, I think he's genuine.
Probably.