Examine source code of Professional Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Professional Gray",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-037-b73f9b34467ba541de861f5b4c0c6316.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(29, 29, 29)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(25, 25, 25)",
      "tab_background_text": "rgb(173, 173, 173)",
      "toolbar_field": "rgb(47, 47, 47)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(49, 49, 49)",
      "popup_text": "rgb(255, 255, 255)",
      "ntp_background": "rgb(43, 43, 43)",
      "ntp_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  }
}