Examine source code of smooth gray

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "gray",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(25, 25, 25)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(25, 25, 25)",
      "tab_background_text": "rgb(131, 131, 131)",
      "toolbar_field": "rgb(25, 25, 25)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(57, 57, 57)",
      "popup": "rgb(25, 25, 25)",
      "popup_text": "rgb(255, 255, 255)",
      "ntp_background": "rgb(25, 25, 25)",
      "tab_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(57, 57, 57)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0311a40b-05f8-4ee2-8042-4546822ca35a}"
    }
  }
}