Examine source code of Blue Checkerboard

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#042338",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Blue Checkerboard",
  "manifest_version": 2,
  "description": "A simple blue checkerboard I created yesterday with The Gimp.\n\nIt makes a nice Firefox theme and comes in different colors which you can find if you browse my profile. Have fun."
}