Strange bottom bar at the end of the site

Hi.

Can you tell me how i get rid of this unwanted grey bar after the last content on my startpage - details see private information field.

I set the background color in the genereal theme for grey, that the impressum site for example has a grey background,like you can see.
But on the startpage the last content had white color and after thr content there is only coming normally the footer. Why is there a unwanted grey bar suddenly?

Greets