Examine source code of Gridded Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Gridded Dark",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-006-51ab495c5f5dde6a3cddb22484acd00d.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(34, 34, 34)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(21, 21, 21)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(47, 47, 47)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(34, 34, 34)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{59205672-689c-408b-9940-bfcdf2ffbccd}"
    }
  }
}