Background color of photo in Photo Grid

Hi all

When you click on an image from a Photo Grid, the image displays full screen with options to cycle backwards and forwards - which is all good. However the background is always White even though i selected Dark Scheme at the Site Wide level. All other backgrounds for all other objects are dark. 

I don't see any properties in the Photo Grid to change background. 

If anyone has an idea it would be appreciated. 

Thanks in advance.