Examine source code of Pattern of squares

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Pattern of squares",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(20, 230, 255, 0.74)",
      "toolbar_text": "rgb(255, 0, 38)",
      "frame": "rgb(26, 212, 179)",
      "tab_background_text": "rgb(255, 6, 6)",
      "toolbar_field": "rgba(21, 197, 123, 0.86)",
      "toolbar_field_text": "rgb(199, 60, 26)",
      "tab_line": "rgb(0, 0, 255)",
      "popup": "rgb(95, 169, 18)",
      "popup_text": "rgb(215, 230, 237)",
      "button_background_active": "rgb(114, 211, 17)",
      "tab_loading": "rgb(0, 0, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ca1a2bb5-239e-41e7-bb98-d05cabdb0012}"
    }
  }
}