Change theme colors

Hello,
I would need the Custom CSS to change the following elements:
– the background color of the text under the posts title (the one with the author name, etc.);
– the background color of the posts footer (the one which contains the social shares options;
– the page footer background color.

I also need the Custom CSS to remove the “Comment n” text under the posts title.

In general, are the Custom CSS to change the theme elements documented? If yes, where can I found this documentation?