There's a lot of aspects to Carol - and perhaps the most interesting from a camera perspective (around POV/voyeurism) are not remarked on here. Nonetheless this piece hopefully lends insight into the film's colour arc (in particular the colour red), and also its use of the train motif.
More could be said of the many green backgrounds that provide counterpoint to the red. (The 9 panel freeze frame that closes the essay is possibly evidence enough that it is pervasive.)
Peg Aloi's essay 'Blink a Bright Red and Green' (artsfuse.org/138953/fuse-film-commentary-blink-a-bright-red-and-green-carols-holiday-charm/) was a useful resource - picking up on the early scene in the car, which I failed to initially.
