It is true, IBMers did wear blue: The Story of MS-DOS

http://www-03.ibm.com/ibm/history/exhibits/waywewore/waywewore_30.html
Within the link you will see slides of the history of the company since its existence in 1911. Funny enough, they did in fact wear blue suits unlike anyone else.

Big Blue is a nickname for IBM. Big Blue refers to a former company dress code that required many IBM employees to wear only white shirts and many wore blue suits. IBM keyboards, typewriters, and some other manufactured devices have played on the "Big Blue" concept, using the color for enter keys and carriage returns. IBM has also used blue logos since 1947.

On August 12, 1981, IBM introduced its new revolution in a box, the "Personal Computer" complete with a brand new operating system from Microsoft and a 16-bit computer operating system called MS-DOS 1.0.

In 1980, IBM first approached Bill Gates and Microsoft, to discuss the state of home computers and Microsoft products. Gates gave IBM a few ideas on what would make a great home computer, among them to have Basic written into the ROM chip. Microsoft had already produced several versions of Basic for different computer system beginning with the Altair, so Gates was more than happy to write a version for IBM.
However, at the time Bill Gates had never written an operating system for new computers and as a result of this Gates recommended that IBM tries another operating system called Control Program for Microcomputers. This system was written by a man named Gary Kildall of Digital Research.
During a meeting with Kildall IBM proposed a contract with him and he refused to sign a non-disclosure agreement. As a result, IBM went back to Gates and Microsoft to ask them to write a new operating system, a system that eventually wiped Kildall's CP/M of use.
This is the story of how the Microsoft Disk Operating System or MS-DOS was created.