I'm going to direct you to Wikipedia for 'Don't Look Now'. Lot's of good info on the movie and discussion of the themes. And I find it pointless to just add more noise for the sake of it. Instead of an essay on themes, I'm going to concentrate on how Richmond and Roeg fill the frame and try to mete out context for their choices.
Above we have two shots from when Laura first meets the old ladies. In the first shot we have a good amount of distance between Laura and them. The ladies are positioned so they are almost one figure. Also notice how the line of sight describes the information process. The blind lady tells her friend and she informs Laura. We catch a bit of the blind lady's reflection in the mirror, a subliminal reference to her spirit-world connection.
Roeg pulls in tight when doing single shots of characters. In the shot above we can only see from her eyes to her chin. It's a bit unsettling, and at the same time gives the blind woman a god-like feel. Her visage dominates our view and hovers above us on the movie screen. She's given a sense of authority. This is one of those times where watching a movie at home hurts the experience.
I found it interesting the way Roeg shot the scene above. In the top picture all three seem close together, stacked on top of each other. But in the bottom shot he makes the gaposis clear, with Laura completely separated. She's also the only image in focus, adding weight to her words. Maybe Roeg was saying something about how Laura perceives her understanding of what the ladies are saying. The second shot shows us she doesn't fully grasp the gravity of her and John's situation.
The use of red is commented on in most reviews. I just wanted to chronicle a couple of prominent examples below.
Below is the sequence which stood out most to me. The low angled shot exaggerates the size of the room. It also exaggerates John's shadow as it looms over the blind lady. She is placed directly beneath the moon, a sly implication of her being a witch.
'Don't Look Now' is a classic horror film which continues to inform movies today, for example 'The Lady In Black'. If you're a fan of the slow burning British horror this is a can't miss. Highly recommended.