Examine source code of christmas theme :D

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "christmas theme :)",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-003-31b6bea3c78e3a19fd889b0389652a94.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(114, 255, 138)",
      "toolbar_text": "rgb(0, 3, 255)",
      "frame": "rgb(255, 112, 112)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgb(136, 141, 144)",
      "toolbar_field_text": "rgb(179, 251, 249)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(225, 253, 255)",
      "popup_text": "rgb(13, 202, 235)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  }
}