Examine source code of Matte Gray Palette

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Matte Gray Palette",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(87, 93, 87)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(59, 60, 59)",
      "tab_background_text": "rgb(229, 229, 229)",
      "toolbar_field": "rgb(59, 60, 59)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(43, 49, 45)",
      "popup": "rgb(27, 40, 45)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(127, 139, 133)",
      "button_background_hover": "rgb(61, 63, 61)",
      "popup_border": "rgb(38, 53, 42)",
      "tab_loading": "rgb(43, 49, 45)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{18b2a86d-854b-49c4-be36-ee47890b34f0}"
    }
  }
}