Examine source code of Gmail Ninja Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Gmail Ninja",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg",
        "images/1.jpg",
        "images/2.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right bottom",
        "right center",
        "left center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat",
        "no-repeat",
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(29, 29, 29, 0.72)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(3, 0, 0)",
      "tab_background_text": "rgb(232, 232, 232)",
      "toolbar_field": "rgba(255, 255, 255, 0.24)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(0, 0, 0)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  }
}