How to set a background color and remove margins?

[SquallLeonhartR]

1. I know how to set the background color but what I don’t know is how to set it like… I set a color but as soon as I save the color becomes default again. So if I for example set it to black in one session, save, and then come back only to find that the color has become white/default as if I never changed it. How do I fix this?

2. Also, margins seem ugly looking to me. How can I remove them>

[mariosv]

This is the Spanish Ask site, Please do you question https://ask.libreoffice.org/c/english/5