Examine source code of custom

{
  "name": "custom",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "spinningskulls.gif"
    },
    "colors": {
      "frame": "rgba(95, 0, 204, 1)",
      "tab_background_text": "rgba(140, 100, 179, 1)",
      "toolbar": "rgba(30, 10, 56, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(255, 255, 255, 1)",
      "toolbar_field_text": "rgba(0, 0, 0, 1)",
      "tab_line": "rgba(95, 0, 204, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2f491402-30f5-4ba6-b59a-1d3e4f163084}"
    }
  }
}