"Border" of the page content area in edit mode is not of the same color as in view mode

This issue refers to the shadows that look like borders that are mentioned in issue XWIKI-21106.

How to reproduce:

• in the color theme:
  • set page content and body background to white
  • in the advanced section, set the xwiki-border-color to purple

    @xwiki-border-color: #ff00ff;
    

• save

Actual result:
View mode:

Edit mode:

The right-hand "separation" in view mode is purple while it's grey in edit mode (hardcoded grey?)

Expected result:

• there is no reason for the color of this separation to be different in edit mode than view mode.