Examine source code of Minecraft_Darkmodus

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Minecraft_Darkmodus",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(114, 121, 124, 0)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(220, 220, 220)",
      "toolbar_field": "rgba(30, 33, 30, 0.8)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(12, 190, 165)",
      "popup": "rgb(27, 40, 45)",
      "popup_text": "rgb(227, 227, 227)",
      "icons": "rgb(253, 253, 253)",
      "tab_loading": "rgb(22, 115, 102)",
      "tab_selected": "rgba(118, 163, 160, 0.64)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d33e62a2-6d90-4cbc-86ee-1f967786e506}"
    }
  }
}