best guess I can personally make is that because Azure literally means “bright blue color of the cloudless sky”
and Microsoft primary logo and branding has long been around the Blue color, they found it apt to name their Cloud service as Azure,
retaining their primary branding color (Blue) and depicting the Cloud (as in Cloudless sky) in the form of a literal word.
why microsoft named their cloud service Azure?
原文：http://www.cnblogs.com/heylinart/p/7669087.html