To get started, navigate to the campaign where you'd like to remove the logo. Then, clicking Settings in the left hand sidebar to open the campaign settings.

Then click Logos in the white label section of the campaign settings menu, to pull up the campaign logos page.

Mouse over the logo you want to remove and click the "X" button that appears.

The logo will be removed immediately, and the campaign will revert to the logo configured in the account-wide level white label settings.