Examine source code of Cool Couple

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Cool Couple",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png",
        "images/1.png",
        "images/2.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top",
        "right top",
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat",
        "repeat",
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0.36)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(142, 179, 201)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(3, 3, 3)",
      "tab_line": "rgb(0, 234, 255)",
      "popup": "rgb(210, 247, 245)",
      "popup_text": "rgb(67, 88, 90)",
      "tab_loading": "rgb(0, 234, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3f99abc5-b824-4504-bf87-b245fc71572f}"
    }
  }
}