I don't think that you can generally say that 'foreshadowing' is illuminating with regard to contextual values. I mean its not a tool specifically related to that. Many things in a text convey values and foreshadowing may but its totally connected to 'what' its foreshadowing. Below is an example of contextual values from Crime Fiction:
The ‘Hard-boiled’ detective, for example, with his wise-cracking, use of muscle, ‘gut’ instinct and ‘street smarts’ can be seen to be almost a complete contrast in the manner in which he derives his evidence but then, he is the product of a completely different context. Throughout the evolution of Crime Fiction there has existed a definite correlation between the values of the detective and the social values of the time. The ‘Hard-boiled’ genre of the 1930-40’s American society can be seen as a response to the horrors of war. The upper-class swells with their private incomes of the Golden Age British Detective fiction were not meaningful to the returned serviceman. A more worldly and cynical detective abandoned intricate puzzles and ingenious deductions and replaced these with rapid action and the brutal reality of urban grime, which translated particularly well into film. In Hawkes’ film, ‘The Big Sleep’ for example, Marlowe predominately uses his intuitive, albeit jaundiced and cynical, knowledge of human behaviour to achieve the resolution of the mystery. In keeping with the sub-genre, Marlowe does what it takes to get the job done despite interfering cops and low-life hitmen. Each new interaction for the pragmatic Marlowe is an opportunity to manipulate, or pressure, a telltale response from a suspect so that an untimely flinch suggestive of a lie is, for Marlowe, a more critical piece of evidence than cigar ash on a carpet. For example, the sequence in Geiger’s Bookshop reveals much about Marlowe’s detection. Having used his intellect carefully in the research of rare books, Marlowe’s whimsical impersonation of a book enthusiast seeking a rare book, is a ruse which reveals to him the shop-girls ignorance of the subject. Checking his ‘hunch’ at the bookstore across the street, he asks the girl if she knows of the same ‘Chevalier Audubon 1840’ to be told, “Nobody would, there isn’t one”, Marlowe replies, “But she didn’t know that”. Through intellect and the careful application of his intimate knowledge of behaviour, Marlowe has immediately established Geiger as a suspect, his shop girl as an accomplice and his bookstore, the front for other nefarious activities thus drawing both Marlowe and the reader deeper into the vortex of the mystery.
So anything in the film which is foreshadowing about the nature of Marlowe and his style would be conveying values of the time. Also, romance, is a new value of this 'hard-boiled' style and becomes almost as important as the crime itself, so early foreshadowing of romantic tension between Marlowe and 'whats-her-name' would be conveying values. This next bit is about 'Cosy' crime fiction:
In the decades following the ‘Hard-boiled’ narrative, the Crime Fiction genre continued to evolve in response to social change by borrowing from the past and yet including sufficient modernity to appeal to a contemporary audience, an audience which was by the 1980’s predominately female. P.D. James, writing in 1982, was influenced by the second wave of Feminism and though a self-acknowledged descendent of Agatha Christie and writing firmly in the ‘Cosy’ or ‘Clue-puzzle’ tradition, brought something very new to British Crime fiction – a female detective. The values of the ‘Cosy’ narrative remains essentially unchanged in ‘The Skull Beneath the Skin’ as it depicts an ordered class system, bourgeois values and suspicion of ‘the outsider’ through it’s use of the ‘closed-circle’ setting. Yet James’ creation of a female detective reflected something new, not only feminist values about the inclusion of women but it also questioned the existing authority of power structures, which are shown by her to be tarnished and corruptible filled with decadence and hypocrisy. Gray has many of the attributes of the ‘Cosy’ detective including shrewdness and a sense of the heroic she is also an amateur, in keeping with the ‘Intuitionists’ values and the novel itself provides a degree of fair play. However, Gray also displays an air of honesty and possibly even incompetence that is far removed from the hard-hitting accuracy of the typical sleuth such as Sherlock Holmes, Hercule Poirot or even Miss Marple.
So again - any foreshadowing in the text that is useful to you is something which gives an early glimpse of these conventions at work.
good luck.
