Examine source code of Muted Retro

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "Muted Retro",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(127, 127, 127)",
      "toolbar_text": "rgb(30, 30, 41)",
      "frame": "rgb(30, 30, 33)",
      "tab_background_text": "rgb(158, 157, 165)",
      "toolbar_field": "rgb(30, 30, 41)",
      "toolbar_field_text": "rgb(123, 127, 204)",
      "tab_line": "rgb(127, 127, 127)",
      "popup": "rgb(49, 49, 49)",
      "popup_text": "rgb(98, 102, 183)",
      "button_background_active": "rgb(98, 102, 183)",
      "button_background_hover": "rgb(97, 91, 106)",
      "frame_inactive": "rgb(49, 49, 49)",
      "icons_attention": "rgb(10, 236, 230)",
      "icons": "rgb(49, 49, 49)",
      "popup_border": "rgb(141, 141, 141)",
      "popup_highlight_text": "rgb(30, 30, 41)",
      "popup_highlight": "rgb(127, 127, 127)",
      "sidebar_border": "rgb(98, 102, 183)",
      "sidebar_text": "rgb(177, 177, 177)",
      "sidebar": "rgb(49, 49, 49)",
      "tab_loading": "rgb(98, 102, 183)",
      "toolbar_bottom_separator": "rgb(49, 49, 49)",
      "toolbar_field_border_focus": "rgb(98, 102, 183)",
      "toolbar_field_focus": "rgb(49, 49, 49)",
      "toolbar_field_highlight_text": "rgb(30, 30, 41)",
      "toolbar_field_highlight": "rgb(127, 127, 127)",
      "toolbar_field_text_focus": "rgb(127, 127, 127)",
      "toolbar_top_separator": "rgb(49, 49, 49)",
      "toolbar_vertical_separator": "rgb(10, 236, 230)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c1dac899-5184-4f14-8e21-fff6f034155a}"
    }
  }
}