Examine source code of pop-os dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "pop-os dark",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat-x"
      ]
    },
    "colors": {
      "toolbar": "rgb(34, 34, 34)",
      "toolbar_text": "rgb(247, 247, 247)",
      "frame": "rgb(54, 54, 54)",
      "tab_background_text": "rgb(156, 156, 156)",
      "toolbar_field": "rgb(54, 54, 54)",
      "toolbar_field_text": "rgb(247, 247, 247)",
      "tab_line": "rgb(166, 234, 236)",
      "popup": "rgb(54, 54, 54)",
      "popup_text": "rgb(247, 247, 247)",
      "tab_loading": "rgb(166, 234, 236)"
    }
  }
}