Examine source code of Space Theme

{
  "name": "Space Theme",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "route-fifty-lead-image.jpg"
    },
    "colors": {
      "frame": "rgba(66, 91, 150, 1)",
      "tab_background_text": "rgba(79, 7, 7, 1)",
      "toolbar": "rgba(78, 93, 166, 0.46)",
      "bookmark_text": "rgba(255, 247, 247, 1)",
      "toolbar_field": "rgba(82, 142, 179, 0.56)",
      "tab_line": "rgba(252, 184, 184, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a536c055-d530-4c80-9db0-72d51d91f082}"
    }
  }
}