After importing using wordpress importer, posts in duotone theme do not pick up background colours from image

Oops, maybe this was a little too obvious. The following works (at least with WordPress 4.2.3).

1. Login to …/wordpress/wp-admin;
2. Go to Posts => All posts;
3. Click on Screen Options;
4. Set “Number of items per page:” to a number greater than the number of posts you have;
5. Click “Apply”;
6. Click on the box at the top left of the list of posts (next to the heading “Title”);
7. On the “Bulk Actions” drop-down menu, select “Edit”;
8. Click “Apply”;
9. You will see a “BULK EDIT” list; do nothing except click on “Update”;
10. After a delay, you will see the All posts page again with the message “xxx posts updated”;

Now the backgrounds will be updated.