Hey everybody! I'll start with a more obvious/recent one.
I felt Frozen did a great job taking a generally monochromatic environment and make it visually engaging. Here is some concept art:
I love how many of these emphasize horizontal and/or vertical lines. (I particularly like the first one with all of the horizontal icicles — gives a cool sense of motion and danger.) I feel their focus with these made the image far more engaging despite the smaller color range.
With the art that had a more muted palette, I felt the most successful ones were when the characters brighter colors were used as the emphasis/focal point of the shot. (Most of these were Anna's purple (?) jacket.)
I feel the coolest use of color in the movie included anything with ice. There's only a few pieces of art that emphasize the ice here, but they showed off a lot of the spectrum with it. There are also a few images here with some muted reds/pinks; they counterbalance all of the whites and blues and generally seem to be focused around the areas of interest in the picture.
One more thing: since we have a mountaineering character in Ram's Horn, I think we should pay particular attention to Kristoff from Frozen — even though he is an ice carver, they probably have similar tools and clothing. Also just a heads up for us to make sure we are not just channeling another version of him for this film.