Low: SemesterSchedule module incorrect color when deleting semester

[lhy-hoyin]

Current: color of the module is kept when returning the module back to the pool of modules during semester delete

Expected: color of the module is reset back to default (i.e. blue) when return back to the pool of modules

Reproduce Bug:

1. Select a course and generate graph/module
2. Under SemesterSchedule, add a new semester
3. Drag a module that needs a prereq to the new semester (eg. CS2100)
4. observe that it turns red
5. delete the previous semester
6. look for that module in the modules pool (i.e. CS2100)
7. BUG: the module is red color