Windows Blue
Windows Blue is the next version of Windows after Windows 8 and rumors suggest that it will be a low-cost or free update to Windows 8. Development of Windows Blue started after its predecessor Windows 8 went RTM. Rumored is that Microsoft will release a Milestone Preview of Windows Blue.
Windows Blue first reported build was 9289 when Microsoft rumored to be finished Milestone 1 of Windows developement. Screenshots show that the build does not have anything visually different from Windows 8. Another build, Windows Blue 9319 shows screenshots of Internet Explorer 11 and a kernel number of 6.3.