Examine source code of Azul :) D

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Kradi",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-011-d53e0d0d1538ed554a90e056a2f04eca.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(7, 139, 168)",
      "toolbar_text": "rgb(247, 253, 251)",
      "frame": "rgb(33, 105, 127)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(239, 239, 239)",
      "toolbar_field_text": "rgb(4, 8, 9)",
      "tab_line": "rgb(255, 244, 0)",
      "popup": "rgb(255, 237, 0)",
      "popup_text": "rgb(5, 5, 5)",
      "tab_loading": "rgb(255, 244, 0)"
    }
  }
}