Examine source code of PESOldSchool

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Clear",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-007-ea06061a8f8be943739a27dace8dc532.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(216, 236, 236)",
      "toolbar_text": "rgb(94, 87, 66)",
      "frame": "rgb(104, 154, 184)",
      "tab_background_text": "rgb(236, 249, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(90, 92, 168)",
      "tab_line": "rgb(248, 112, 140)",
      "popup": "rgb(177, 211, 227)",
      "popup_text": "rgb(89, 82, 71)",
      "tab_loading": "rgb(248, 112, 140)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2039fb25-7b3c-42c4-b892-f41c9574f03d}"
    }
  }
}