Examine source code of Sublimely Obsidian

{
  "theme": {
    "images": {
      "theme_frame": "ff-head-dark.jpg"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Sublimely Obsidian",
  "manifest_version": 2,
  "description": "This is a dark theme that works best in OSX with zero to one toolbars.  Enjoy"
}