Examine source code of inSign theme

{
  "manifest_version": 3,
  "version": "1.2",
  "name": "inSign theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(240, 243, 246, 0)",
      "toolbar_text": "rgb(62, 63, 66)",
      "frame": "rgb(240, 243, 246)",
      "tab_background_text": "rgb(62, 63, 66)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(62, 63, 66)",
      "tab_line": "rgb(222, 222, 222)",
      "popup": "rgb(245, 245, 245)",
      "popup_text": "rgb(62, 63, 66)",
      "button_background_active": "rgb(238, 238, 238)",
      "button_background_hover": "rgb(213, 219, 226)",
      "icons": "rgb(62, 63, 66)",
      "sidebar_border": "rgb(238, 238, 238)",
      "tab_selected": "rgb(255, 255, 255)",
      "tab_loading": "rgb(222, 222, 222)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "insign_theme_1.2@getinsign.de"
    }
  }
}