Examine source code of Proton Dark (FF Theme)

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Proton Dark (FF Theme)",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(33, 33, 39)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(33, 33, 39)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(46, 46, 54)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(66, 65, 77)",
      "popup": "rgb(46, 46, 54)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_hover": "rgb(66, 65, 77)",
      "ntp_background": "rgb(33, 33, 39)",
      "popup_border": "rgb(46, 46, 54)",
      "tab_selected": "rgba(66, 65, 77, 0.75)",
      "toolbar_bottom_separator": "rgb(33, 33, 39)",
      "toolbar_field_border": "rgb(50, 49, 58)",
      "toolbar_field_separator": "rgb(33, 33, 39)",
      "toolbar_top_separator": "rgb(33, 33, 39)",
      "tab_loading": "rgb(66, 65, 77)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{19a7e3fe-e4ec-41cf-8444-e546e3e3ce92}"
    }
  }
}