Examine source code of grayminimal

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "grayminimal",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(36, 36, 36)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(36, 36, 36)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(36, 36, 36)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(36, 36, 36)",
      "popup": "rgb(36, 36, 36)",
      "popup_text": "rgb(255, 255, 255)",
      "ntp_background": "rgb(36, 36, 36)",
      "toolbar_bottom_separator": "rgb(36, 36, 36)",
      "toolbar_field_border_focus": "rgb(36, 36, 36)",
      "toolbar_top_separator": "rgb(36, 36, 36)",
      "tab_loading": "rgb(36, 36, 36)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3be22c76-0c2e-4892-852e-e5443c838d17}"
    }
  }
}