Are you trying to change the css or scss? Also have a look at Customize Styling Using Calypso - Studio Pro 8 How-to's | Mendix Documentation on how to use calypso to change your styling.
Hope this helps!
Do i understand it correctly if the changes are visible locally for you, but not for the other users on their pc's?
What exactly did you change in the scss file?
If you added new fonts, pictures or other kinds of styling, you could try to implement these in the deployment folder/ theme as well.
It can be that your app is searching for a "local” file which is not available on the pc's of the other app users.