OK, I saw Begins in IMAX last night. Yes, it's obviously a DMR blowup with degraining and sharpening, but the color still matches up with my memories of seeing it in theaters 10 years ago.
I remembered the film looking brown and gold, but screenshots of the DVD and Blu-ray, while having the brown/gold look, show a more neutral and varied palette. That's not the case with the IMAX print - almost everything is pushed to either brown/gold or teal/cyan, just as I remembered from the original run.
The DVD palette looks closER?, but skin tones on the Blu look too pink. Everyone's skin was quite bronze on the IMAX print. It was also a lot more contrasty than the video transfers, though that is the case with all theatrical prints of anything compared to home media...