Examine source code of Simple Dark

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "Simple Dark",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(17, 16, 20)",
      "toolbar_text": "rgb(229, 228, 231)",
      "frame": "rgb(12, 11, 14)",
      "tab_background_text": "rgb(229, 228, 231)",
      "toolbar_field": "rgb(7, 7, 8)",
      "toolbar_field_text": "rgb(229, 228, 231)",
      "tab_line": "rgb(48, 46, 56)",
      "popup": "rgb(12, 11, 14)",
      "popup_text": "rgb(229, 228, 231)",
      "button_background_active": "rgba(36, 34, 42, 0.75)",
      "button_background_hover": "rgba(36, 34, 42, 0.5)",
      "frame_inactive": "rgb(12, 11, 14)",
      "icons_attention": "rgb(143, 176, 239)",
      "ntp_background": "rgb(12, 11, 14)",
      "ntp_text": "rgb(229, 228, 231)",
      "popup_border": "rgb(29, 27, 34)",
      "sidebar_border": "rgb(29, 27, 34)",
      "sidebar": "rgb(12, 11, 14)",
      "tab_selected": "rgba(36, 34, 42, 0.5)",
      "toolbar_bottom_separator": "rgb(29, 27, 34)",
      "toolbar_field_border_focus": "rgb(143, 176, 239)",
      "toolbar_field_highlight": "rgb(32, 96, 223)",
      "tab_loading": "rgb(48, 46, 56)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b6c2b2f2-0b81-475a-bc3b-174f98f2236e}"
    }
  }
}