Examine source code of Darker gray

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "colloid black",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(15, 15, 15)",
      "toolbar_text": "rgb(190, 190, 190)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(160, 160, 160)",
      "toolbar_field": "rgb(0, 0, 0)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(33, 33, 33)",
      "popup": "rgb(21, 21, 21)",
      "popup_text": "rgb(180, 180, 180)",
      "tab_loading": "rgb(33, 33, 33)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8e8b33ff-9968-4e0e-a631-e3b256a856ee}"
    }
  }
}