Sheet version comparison is a feature available on premium Fieldwire accounts. It allows you to compare the changes in design between versions of your plans. The more recent version's revisions will appear highlighted in red, while the designs that were removed from the older version will appear in blue.
To compare your sheet versions, just open up a plan on web and click the version description button in the bottom right corner. You can then select "Compare," which will prompt you to select the two versions that you wish to compare. You can also select the "Compare" feature by clicking on the "Actions" button directly above the opened plan.
You'll then see the newer drawing components in red, and the older/former ones in blue.