Examine source code of Source VGUI

{
  "name": "Source VGUI",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "vgui.png"
    },
    "colors": {
      "frame": "rgba(85, 85, 85, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(118, 118, 118, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(0, 0, 0, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(176, 176, 176, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fa37465c-ab21-4b8e-b6e9-ef6b721097ba}"
    }
  }
}