Examine source code of Mattblack (Dark)

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "olem theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(34, 34, 34)",
      "toolbar_text": "rgb(219, 219, 219)",
      "frame": "rgb(18, 18, 18)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(47, 47, 47)",
      "toolbar_field_text": "rgba(255, 255, 255, 0.77)",
      "tab_line": "rgb(56, 56, 56)",
      "popup": "rgb(47, 47, 47)",
      "popup_text": "rgb(217, 217, 217)",
      "icons_attention": "rgb(231, 231, 231)",
      "ntp_background": "rgb(18, 18, 18)",
      "popup_border": "rgb(47, 47, 47)",
      "toolbar_field_border_focus": "rgb(176, 176, 176)",
      "toolbar_vertical_separator": "rgb(107, 107, 107)",
      "tab_loading": "rgb(56, 56, 56)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{434a875f-1c45-491c-87ca-9ac13a30ae7e}"
    }
  }
}