If you are experiencing a black screen after finishing a picture in Zen Color on your iPad, here are the steps you can follow to potentially resolve the issue:

1. Force Close Zen Color:
- Swipe up from the bottom of the screen (or double-click the Home button if your iPad has one) to open the App Switcher.
- Find the Zen Color app and swipe it away to force close it.

2. Restart Your iPad:
- If force closing the app doesn't work, you can try restarting your iPad again. To do this, press and hold both the Lock button and the Volume Down button until you see the slider. Slide to power off your iPad. After it turns off, press the Lock button again to turn it back on.

3. Clear App Cache (if applicable):
- Sometimes, storing unnecessary data can cause issues. If you are able to access settings in Zen Color, look for an option to clear cache or clear app data.

4. Delete and Reinstall Zen Color:
- If the issue persists, consider uninstalling the app. Press and hold the Zen Color app icon until it jiggles, then tap the "X" or "Remove App". After uninstalling, go to the App Store and reinstall Zen Color.

5. Check for App Updates:
- Make sure that you have the latest version of Zen Color. Open the App Store, go to the "Updates" section, and update the app if any updates are available.

6. Manage In-Progress Pictures:
- The issue may be tied to specific images. If you can access your gallery in Zen Color, consider deleting any in-progress pictures and starting a new one to see if the problem resolves - learn more.

7. Contact Support:
- If none of the above steps work, it may be beneficial to contact Zen Color's support for further guidance. You can visit their help center or reach out via their social media for specific troubleshooting related to your issue.

Following these steps should help you identify and resolve the black screen issue in Zen Color. If the problem continues, it may require more specialized support from the app developers.