Examine source code of Blue Dark

{
  "name": "Blue Dark",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "transparent-bg-firefox-theme.png"
    },
    "colors": {
      "frame": "rgba(47, 73, 143, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(31, 40, 74, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(47, 73, 143, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{616bf474-d46c-4e74-ab67-8cd228d35162}"
    }
  }
}