From one of the comments on that blog post:
Jens says:
November 15, 2012 at 02:07

They are essentially just tweaked using Designers palette editor. Just open a form in designer and click on the palette section. Alternatively you can try the built-in palette by doing qApp->setPalette(style()->standardPalette()).
Unfortunately the conversation only reveals the colours (approx) used for the dark variant:
Jens says:
January 9, 2013 at 11:18

I dont have the original but you should be able to get close by just setting these colors I found using the colorpicker tool:
window/button: #353535
highlight: #8e2dc5

The main trick to making your own color schemes is to use gray or only very low saturation on the background color. For the highlight color you can be a bit more bold but avoid strong primary colors like full red or yellow. Follow those rules and almost all the schemes look reasonably well.
You could just sample the colours from the screenshot image in gimp or something like that.

The legacy styles can be had from git:
https://codereview.qt-project.org/#q...yleplugins,n,z
http://qt.gitorious.org/qt/qtstyleplugins