Windows 8.1 on a physical PC. But these particular code points may not be part of the System font used for windows by Windows 7. Windows 8.1 maybe able to fetch characters from another font, which Windows 7 may not.
There are several mentions of API methods, but none posted, and from the tone people did not seem too sure about what they were writing.
But there is a very interesting idea there : use a plain box window and fake the regular controls. That would indeed allow placing whatever you want in the pseudo window bar, including a color icon.