Some of the themes in our Design Settings library add a filter to your images in your project for visual consistency. If the current filter doesn't fit the look and feel of the video you are creating, you can turn that off!
You can remove the filter by clicking on the Design icon at the top of the Workspace. Select Video Style from the tabs in the Design Settings menu. Scrolling down to the bottom of the menu, select NONE under filters. That should clear up the filter from your photos! You will need to export your video again for the settings to save.