This is an oft debated topic among the editorial circles. While some publishers have either conveniently or deliberately or rather forcefully chosen US English (referred as the corrupt version) in the interests of larger audience, there are a few purists who are following the British format (referred as the correct version), occasionally criticizing the former.  

As a school kid, I always wondered why there were unnecessary letters put in a number of words. It doesn't damage if you ignore me from programme and similarly u from colour. Even my English teacher used to pass that question and continued teaching the purists way.

Globalization further complicated things when I started finding American spellings in a few books, especially computer science books. I approached my English lecturer who introduced me to American English and said that's not accepted in India. I was fascinated by the amount of customization done by the Americans and started developing a special liking for it. Since then I struggled with the placement of s and z in a number of words, until I joined my first job.

My first job as Research Associate at Icfai Center for Management Research wanted me to employ US English. Microsoft Word and access to the Internet made my job easier and I started using American English everywhere.

My next job at the recently demised Ochre Media Pvt. Ltd (erstwhile SPG Media Pvt. Ltd.) demanded that I use British English though a majority of our clients resided in North America. To persuade my penchant for American English, I have been incorporating as many American spellings as possible in my blog. Of course, I used to deliberately ignore a few American spellings at my workplace which were often identified and rectified by my colleague Ramakrishna Sadhu, a member of purists school .