Examine source code of Old dark theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Old dark theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-021-775b159da029a74f5c76e835cd65e9dc.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(50, 50, 50)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(12, 12, 12)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(71, 71, 71)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(10, 132, 255, 0)",
      "popup": "rgb(50, 50, 50)",
      "popup_text": "rgb(255, 255, 255)",
      "ntp_background": "rgb(50, 50, 50)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_highlight": "rgb(136, 136, 136)",
      "toolbar_field_border_focus": "rgb(136, 136, 136)",
      "toolbar_field_highlight": "rgb(136, 136, 136)",
      "toolbar_top_separator": "rgb(50, 50, 50)",
      "tab_loading": "rgba(10, 132, 255, 0)"
    }
  }
}