Yes. Your app is automatically updated with your new content, as well as new colors and new design options.
The only things that would require new submissions are items related to the app itself:
- app icon,
- app startup image (splash screen),
- app name,
- app description,
- categories and keywords,
- and the mobile website url (in settings>domain), if you change it after your app is published.
If you add new page in your app after it has been published. Only these pages would require to submit the app again if you don’t have to add them before publishing:
- Audio & Radio page (you can add them after your app is published but it will not work in background when the app is closed)
- Scan Code
- AdMob for iOS (For Android you can add AdMob banners or interstitals after your app is published, but iOS will need new publication
But, adding or changing content of the pages after your app has been published doesn’t require to publish again.