The application form that Meg fills out for the poetry contest says her poem is entitled "Blue Car", although at that point she has not yet written the poem or given it a title.
When Mr. Auster is standing on the beach talking to Meg, his collar alternates between straightened and not straightened.
When Meg changes to join Auster and family on the beach, she has on a red bikini and over it, a red sweater. She has the sweater on when she gets there. But later, when Auster asks to "walk her home," she does not have the sweater, and Auster has to lend her his gray sweater to keep her warm.
When Angus's dad starts the car at the end, it clearly does not turn over completely and start up.