I would like to highlight any changes made to a long list of form checkboxes. That way the user can review all the changes made (whether checked or unchecked) before saving. Are there any examples for checkbox dirty states? I looked at material design and there is no mention there. Any ideas?
Use a combination of versioning and element styling to highlight the changes. Since the case is, "As a user I want to learn about what's changed by myself and others", you might have a "Show changes since last login" mode that highlights each changed item - could be a background color on the checkbox and label, could be a different color font, could be a dotted line box around the changes - I'd play around and see what looks good. Perhaps the user can hover on the changed items to see who made the change. Perhaps you can include full versioning to see which changes were made each time the form was altered.
You can use a different styling on newly checked items to differentiate them from previously checked items, such as different background color, borders, or font weight. For example, you can use a background color same as or similar to the background color of the 'Save' button. That way you will be correlating updates to the saving action.