Examine source code of The big R theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "My theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-021-775b159da029a74f5c76e835cd65e9dc.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(0, 0, 125)",
      "toolbar_text": "rgb(11, 113, 255)",
      "frame": "rgb(255, 0, 1)",
      "tab_background_text": "rgb(215, 226, 239)",
      "toolbar_field": "rgb(54, 58, 89)",
      "toolbar_field_text": "rgb(0, 255, 0)",
      "tab_line": "rgb(255, 0, 4)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(0, 89, 194)",
      "button_background_active": "rgb(234, 27, 27)",
      "icons": "rgb(255, 255, 255)",
      "tab_loading": "rgb(255, 0, 4)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{981d0231-b6d5-4f41-bd63-d50d2b6fa3dc}"
    }
  }
}