Examine source code of Black Concrete

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Black Concrete",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(42, 42, 42)",
      "toolbar_text": "rgb(190, 190, 190)",
      "frame": "rgb(31, 31, 31)",
      "tab_background_text": "rgb(219, 219, 219)",
      "toolbar_field": "rgb(219, 219, 219)",
      "toolbar_field_text": "rgb(0, 116, 181)",
      "tab_line": "rgb(0, 164, 255)",
      "popup": "rgb(129, 129, 129)",
      "popup_text": "rgb(31, 31, 31)",
      "tab_loading": "rgb(0, 164, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b6e38029-4045-4c0f-835e-63fec766424d}"
    }
  }
}