Examine source code of Simple Greyscale

{
  "manifest_version": 2,
  "version": "1.2",
  "name": "Simple Greyscale",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(34, 34, 34)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(15, 15, 15)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(51, 51, 51)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(234, 118, 203)",
      "popup": "rgb(68, 68, 68)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(85, 85, 85)",
      "button_background_hover": "rgb(68, 68, 68)",
      "icons_attention": "rgb(50, 205, 50)",
      "icons": "rgb(255, 255, 255)",
      "ntp_background": "rgb(34, 34, 34)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_border": "rgb(68, 68, 68)",
      "popup_highlight_text": "rgb(255, 255, 255)",
      "popup_highlight": "rgb(0, 119, 255)",
      "sidebar_border": "rgb(68, 68, 68)",
      "sidebar_highlight_text": "rgb(255, 255, 255)",
      "sidebar_highlight": "rgb(102, 102, 102)",
      "sidebar_text": "rgb(255, 255, 255)",
      "sidebar": "rgb(34, 34, 34)",
      "tab_selected": "rgb(34, 34, 34)",
      "toolbar_bottom_separator": "rgb(68, 68, 68)",
      "toolbar_field_border_focus": "rgb(234, 118, 203)",
      "toolbar_field_focus": "rgb(68, 68, 68)",
      "toolbar_field_highlight_text": "rgb(255, 255, 255)",
      "toolbar_field_highlight": "rgb(0, 119, 255)",
      "toolbar_field_separator": "rgb(68, 68, 68)",
      "toolbar_top_separator": "rgb(68, 68, 68)",
      "toolbar_vertical_separator": "rgb(68, 68, 68)",
      "tab_loading": "rgb(234, 118, 203)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{430722b4-f91e-4927-b7ac-2ec14b03d257}"
    }
  }
}