Examine source code of Poke Your Balls

{
  "theme": {
    "images": {
      "theme_frame": "Pokeball4.png"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#000"
    }
  },
  "version": "2.0",
  "name": "Poke Your Balls",
  "manifest_version": 2,
  "description": "If you like balls then you'll love this elegant yet stylish and discreet Pokeball theme. None of your friends will even know that you still love Pokemon at the age of 20."
}