@Flow If you are using the pro version, for the body background color you can go to Appearance->Theme Options->Design Options Tab->Color Options. You can change the body(content) background color there and click on ‘Save all Changes’.
For the header background color, you can use the custom css for this. You can go to Appearance->Theme Options->Design Options Tab->Custom CSS. Pate the following css and click on ‘Save all Changes’.
#branding {
background-color: #DDDDDD;
}
You can change the color code your liking. You can look for the color codes in this link http://www.colorpicker.com/.
About your last question, it will need coding and css customization which can take some effort. As this is like a new feature to be added you will have to hire a developer for this.