Joy,
i haven't seen the movie but have seen the previews and from what I remember the colors on Vanessa Redgrave were beautiful IMO. I think that grey haired women look beautiful with muted cool tones. It is a very elegant and romantic look. I would probably dress in those colors if I had grey hair. I do not think all grey-haired women need to go that route. It all depends on hairstyle, skin tone, overall style preference and personality (of course). For instance, I can picture a sharp woman with a short stylish hairdo wearing black, white and red or some other bright with the grey of her hair being a neutral. This would be on someone with graphic, features and a modern, minimal sensibility. On the other hand, a women with longer, wavy or curly, layered grey hair would look better in softer more muted tones. That is probably why I think I would like those colors. I think if Angie went grey she would be very graphic and still wear contrast. (I could be totally off but I am just picturing her with a white grey punky hairdo and black and white Chanel with pearls).
I also think that only certain women look right in grey hair. If you have warm skin tones, usually your hair is a kind of dull grey. If you have cool skin often you get that beautiful shock of a white grey that is stunning. My sister in law has hair like that and she wears lots of red, fuchsia and blue. Looks fab!
As usual, there are many variables and not one answer. I want to see that movie. I love the colors that Vanessa Redgrave wore in Camelot. (I copied her look for my wedding.)