Examine source code of f4u_2021

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "f4u_2021",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(23, 80, 115)",
      "toolbar_text": "rgb(238, 239, 245)",
      "frame": "rgb(142, 179, 201)",
      "tab_background_text": "rgb(4, 4, 4)",
      "toolbar_field": "rgb(245, 241, 223)",
      "toolbar_field_text": "rgb(4, 4, 4)",
      "tab_line": "rgb(179, 24, 56)",
      "popup": "rgb(250, 247, 234)",
      "popup_text": "rgb(55, 58, 93)",
      "tab_loading": "rgb(179, 24, 56)"
    }
  }
}