I have used chrome inspector... From my testing, I think I will have to use a plugin gallery like jetpack's or something. The native gallery uses some of the page post css. Using the example above:
I was able to change the background color without affecting my page text area.
Because I set a padding on
to move text away from the container wall
The white padding area still remains with the native gallery. It uses the same css.
So I still have the problem of having white where I don't want it. I need the padding for my page text. The native media gallery uses it to when I don't want it to.
I'm guessing that if I use a different gallery plugin, there will be different css I can target for this area, and eliminating the problem with my page text input area.
We will see.... I wish WordPress would of gave a little more css control with their native gallery.