Examine source code of Deep Purple :D

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "DeepPurple",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg",
        "images/1.jpg",
        "images/2.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "left center",
        "left center",
        "right center"
      ],
      "additional_backgrounds_tiling": [
        "repeat",
        "no-repeat",
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(223, 187, 218, 0.27)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(223, 187, 218)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgba(255, 255, 255, 0.72)",
      "toolbar_field_text": "rgb(56, 24, 62)",
      "tab_line": "rgba(221, 190, 239, 0.81)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(53, 22, 58)",
      "ntp_background": "rgb(173, 135, 179)",
      "sidebar_border": "rgb(223, 187, 218)",
      "tab_loading": "rgb(223, 187, 218)",
      "tab_selected": "rgba(53, 22, 58, 0.61)",
      "tab_text": "rgb(255, 255, 255)",
      "toolbar_bottom_separator": "rgb(221, 190, 239)",
      "toolbar_field_border": "rgb(221, 190, 239)",
      "toolbar_top_separator": "rgb(221, 190, 239)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e0918804-0b03-497f-bcea-2c9f06dc4d3e}"
    }
  }
}