Not much is known about Microsoft's upcoming "Windows Blue", but if a couple of recent job postings are any indication, the secretive project will introduce user interface and experience "improvements", particularly in relation to the Windows Start Screen, windowing and customization features.

Based on the most recent information available, Windows Blue should be more akin to a service pack than a full-fledged successor to Windows (i.e. *not* Windows 9), but will encompass more products than just its desktop OS. The project is believed to be the precursor to more rapid and incremental Windows-family update schedule, possibly even setting the stage for a future subscription model. 

Windows Blue is expected to bring numerous tweaks and improvements to various aspects Windows 8, Windows RT, Windows Phone 8 and Windows 2012 Server. Additionally, the update is rumored to introduce changes to Microsoft's peripheral services, such as SkyDrive and

The February 15 job posting for a software engineer was found here, although it was recently taken down -- presumably Microsoft either filled the position or didn't like the attention. According to ZDNet's Mary Jo Foley, the posting read:

We're looking for an excellent, experienced SDET to join the Core Experience team in Windows Sustained Engineering (WinSE). The Core Experience features are the centerpiece of the new Windows UI, representing most of what customers touch and see in the OS, including: the start screen; application lifecycle; windowing; and personalization. Windows Blue promises to build and improve upon these aspects of the OS, enhancing ease of use and the overall user experience on devices and PCs worldwide."

Although that particular position has since been removed, another interesting "Windows Blue" job offering cropped up: a development lead for Excel MX. In the job post, Excel MX is billed as a "high quality Excel app for Windows Phone Blue".

Rumors suggest Blue's launch could happen as soon as this year, with all platform releases occurring around the same time.