Examine source code of Tropics

{
  "theme": {
    "images": {
      "theme_frame": "firefox3.jpg"
    },
    "colors": {
      "frame": "#1755b3",
      "tab_background_text": "#fffee3"
    }
  },
  "version": "2.0",
  "name": "Tropics",
  "manifest_version": 2,
  "description": "Tropical palm trees and water"
}