Back in February, Microsoft wrote a blog post explaining how Windows 8 & Windows RT will support various languages. Several paragraphs in that post deal with the English language, here's the main one.
"We are proud to announce the addition of English for the United Kingdom to the list of Windows display languages. We admit that this is something we should have done a long time ago. Windows users in the UK have gotten by with the US English version of Windows, and while we Americans knew this was not their favourite, that is clearly no defence. We believe that this version of Windows will also be widely used in India, Australia, South Africa, New Zealand, the Republic of Ireland and many other places.
Well, Microsoft has finally made these language packs available, so if you live in the UK, Ireland, Australia, New Zealand, India, South Africa, Singapore or Hong Kong and you want Windows to use the word "Colour" instead of "Color" on system dialogs and built in applications, then this is just a quick article which will explain how to install and activate this language pack.