Examine source code of Plain, Simple, Gray

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#f2f2f2",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Plain, Simple, Gray",
  "manifest_version": 2,
  "description": "This is a theme I created for myself. When I looked for a simple gray theme I couldn't find any, so I made this one."
}