Change background of single page

Site URL: https://rawrandthelike.com/nft

How do I change the background color of a single page of my site? 

How would I change the color of the text?

Also: How could I remove the padding between images from a Gallery Block?

Background for main content or both header + Footer. If main content, add this to Design > Custom CSS

/* homepage background */
body#collection-60afc82524f48376a66d5068 .Main {
    background: red;
}