Examine source code of Best dark theme ever

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Best dark theme ever",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(49, 49, 49)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(72, 72, 68)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(31, 33, 33)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(49, 49, 49)",
      "popup": "rgb(49, 49, 49)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(49, 49, 49)",
      "frame_inactive": "rgb(73, 73, 73)",
      "ntp_background": "rgb(27, 27, 27)",
      "popup_border": "rgb(31, 33, 33)",
      "popup_highlight": "rgb(55, 56, 58)",
      "sidebar_border": "rgb(49, 49, 49)",
      "sidebar_text": "rgb(249, 249, 249)",
      "sidebar": "rgb(38, 36, 36)",
      "tab_selected": "rgb(49, 49, 49)",
      "toolbar_bottom_separator": "rgb(49, 49, 49)",
      "toolbar_field_border_focus": "rgb(104, 104, 104)",
      "toolbar_field_border": "rgb(31, 33, 33)",
      "toolbar_field_highlight": "rgb(83, 102, 133)",
      "toolbar_top_separator": "rgb(49, 49, 49)",
      "tab_loading": "rgb(49, 49, 49)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d0502c59-532c-49b5-9880-adf064400d19}"
    }
  }
}