Examine source code of Eternal Emerald Green

{
  "name": "Eternal Emerald Green",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "3000×200Firefox2020年4月分(完成形・5ae3d1・350dpi).jpg"
    },
    "colors": {
      "frame": "rgba(228, 252, 248, 1)",
      "tab_background_text": "rgba(3, 87, 85, 1)",
      "toolbar": "rgba(255, 255, 255, 0.2)",
      "bookmark_text": "rgba(3, 87, 85, 1)",
      "toolbar_field": "rgba(255, 255, 255, 0.2)",
      "toolbar_field_text": "rgba(3, 87, 85, 1)"
    }
  }
}