If there's any doubt that the Windows client team is laser-focused on the coming Blue refresh of Windows 8, a new Microsoft job post makes it even plainer.

A February 15 post for a software development engineer in test on the Microsoft Careers site (to which Charon at Ma-config.com alerted me), mentions "Windows Blue." According to that posting, the Core Experience team in Windows Sustained Engineering (WinSE) is involved in making improvements to the start screen, application lifecycle, windowing and personalization. Windows Blue will "build on and improve" these OS components, the posting says.

Here's an excerpt:

"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."

Blue is the codename for the next wave of Windows-related operating system and services updates from Microsoft, according to my contacts. There will be a Blue update to Windows 8, Windows Server 2012, Windows Phone 8 and the Windows Services like Hotmail and SkyDrive -- all of which are slated to wash up in roughly the same timeframe, my sources have said. Last year, one tipster told me Microsoft was aiming to deliver Windows Blue around late summer 2013 .

Blue isn't simply a fancy new name for a service pack. With Blue, Microsoft is working to transition to a more rapid update pace.

On the Windows and Windows Phone fronts, Blue is expected to include new features and even new programming interfaces designed to bring the different flavors of Windows closer together, from an app model/development model perspective . That said, it's not just Windows internals that will be updated with Blue. As the job posting above verifies, user interface and experience updates will be part of Blue, too.

Microsoft officials have declined to comment on Blue. It's unknown what Microsoft officially will name Blue once it's released, but it's likely to be positioned as a refresh to Windows 8, not a whole new version of Windows (like a Windows 9), I continue to hear.

By the way, there are plenty of mentions of "blue" on Microsoft's career site that have nothing to do with the coming Blue wave/refresh." Blue links," "blue screens" and "wavy blue lines" all show up -- and have nothing to do with the upcoming Blue refresh.

Update: @h0x0d (Walking Cat on Twitter) just found a Microsoft job reference to Windows Phone Blue, too. Here's his screen shot of it:

As he notes, there's also a reference to "Excel MX" in that job post. Excel MX is likely a not-yet-delivered, fully touch-optimized and Metro Style/Windows Store version of Excel -- similar to the OneNote MX and Lync M X versions of two of Microsoft's Office apps that are in the Windows Store now.