Set up correctly background color on custom content Impulse theme

[DFU98]

I want the div in the html section of the custom section to have a gray background color but it isn't the same size as the image one.

If I use this CSS

.custom-content {
  background-color: gray;
}
.custom__item {
  margin: 0px;
  padding: 0px;
}

It looks like this

That looks close enough as what I have in mind, that is the html section to has a background color and it matching the image section one but as you can see there is a bit of gray background below the image.

What should I do to make the gray below dissapear? Also if there is a way to do it better with CSS without removing margins and padding I would appreciate it.