Inconsistent Remove Message Colors

### Issue
When removing a supervisor from a department in a department modal on the Manage Departments page under the Administration tab in the sidebar, The flash message is green. This is inconsistent with the red flash messages that show up elsewhere in the website when doing a remove.

### Testing

**The Page**

**Click on a department name then then add a supervisor, note that the flash message when you add them is green**

**Click 'Remove next to the supervisor's name, note that the flash message is also green**