how do I remove synced photos from my iphone 6?

Hey 4D4,

Thanks for the question. If I understand correctly, you want to delete synced photos. I would recommend that you read this article, it may be able to help the issue.

Sync photos to your iPhone, iPad, and iPod touch in iTunes - Apple Support

Delete synced photos

1. In iTunes, locate and click on your device.
2. Click Photos.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.

Learn how to delete photos and video synced from iTunes when you can't access the originals.

Thanks for using Apple Support Communities.

Have a good one,

Mario