Problem Description

I want all reference files to display gray so the elements in the active file stand out.

Steps to Resolve

1. Go to File - Settings - Configuration - Configuration Variables.
2. Click on the Levels category.
3. Edit MS_LEVEL_EDIT_NESTED_ATTACHMENT_LEVELS and give it a value of 1.
4. Click OK on the Configuration Variables dialog and Yes to Save the configuration changes.
5. Exit the file and re-open it and you should be able to set Override colors on nested reference files.