Examine source code of Excalibur Umbra

{
  "manifest_version": 2,
  "version": "2.0",
  "name": "Excalibur Umbra",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(44, 46, 47)",
      "toolbar_field": "rgb(56, 62, 65)",
      "toolbar_field_text": "rgb(164, 156, 113)",
      "tab_line": "rgb(164, 156, 113)",
      "popup": "rgb(34, 35, 36)",
      "popup_text": "rgb(251, 93, 6)",
      "tab_loading": "rgb(164, 156, 113)",
      "bookmark_text": "rgb(147, 211, 217)",
      "frame": "rgb(57, 60, 65)",
      "tab_background_text": "rgb(164, 156, 113)"
    }
  }
}