Examine source code of Yellowbox

{
  "name": "Yellowbox",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "2048px-Color_icon_yellow.svg.png"
    },
    "colors": {
      "frame": "rgba(247, 207, 10, 1)",
      "tab_background_text": "rgba(250, 130, 130, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4bb65906-28d6-42e1-bd37-49b2c055c204}"
    }
  }
}