[daxitude]

1 - (edit) I found it. It's defined by {vb:stylevar navbar_tab_background.backgroundColor}

2 - This is defined by css property .wgo_block .blockhead. The background is set by {vb:stylevar secondarycontent_header_background}. Tested on my forum and this works.

3 - This is the post header? If so StateCollapse is correct: {vb:stylevar postbithead_background}

4 - This is {vb:stylevar link_color}

Whenever I can't find a stylevar I use developer tools in Google Chrome or Firebug in Firefox to Inspect Element, find the relevant css property, search templates for that css property, and figure out which stylevar is styling it. In some cases I've found goofy settings where you think there should be a stylevar and have ended up editing the css to get the desired effect.