Examine source code of Hender's Theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "basic1",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-034-e0dfa84411058d2e5627f19f1ea501ca.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(31, 98, 211)",
      "toolbar_text": "rgb(243, 185, 213)",
      "frame": "rgb(62, 31, 129)",
      "tab_background_text": "rgb(244, 93, 255)",
      "toolbar_field": "rgb(20, 78, 178)",
      "toolbar_field_text": "rgb(243, 185, 213)",
      "tab_line": "rgba(124, 53, 162, 0)",
      "popup": "rgb(62, 31, 129)",
      "popup_text": "rgb(243, 185, 213)",
      "tab_background_separator": "rgba(124, 53, 162, 0)",
      "tab_selected": "rgb(42, 19, 91)",
      "tab_text": "rgb(244, 93, 255)",
      "toolbar_bottom_separator": "rgb(55, 142, 187)",
      "toolbar_top_separator": "rgb(31, 98, 211)",
      "tab_loading": "rgba(124, 53, 162, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f59ab1d9-b6d2-4fc3-9ac1-6c69488fd9fb}"
    }
  }
}