Examine source code of silksong dark

{
  "manifest_version": 2,
  "version": "1.2",
  "name": "silksong dark 1.2",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(34, 17, 27)",
      "toolbar_text": "rgb(254, 45, 86)",
      "frame": "rgb(10, 13, 21)",
      "tab_background_text": "rgb(254, 45, 86)",
      "toolbar_field": "rgba(84, 24, 44, 0.95)",
      "toolbar_field_text": "rgb(241, 206, 195)",
      "tab_line": "rgb(254, 45, 86)",
      "popup": "rgba(84, 24, 44, 0.95)",
      "popup_text": "rgb(241, 206, 195)",
      "sidebar_border": "rgb(65, 27, 36)",
      "sidebar_highlight": "rgb(38, 18, 30)",
      "sidebar": "rgb(21, 15, 24)",
      "tab_selected": "rgb(80, 5, 19)",
      "tab_loading": "rgb(254, 45, 86)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f67e21a8-7306-430c-bdbd-f79d84af4152}"
    }
  }
}