The values differ because the rgb-values of the color picker aren't gamma corrected.
If I correct them like answered here https://stackoverflow.com/a/17910665/3069477 the colors are matching. I still get different RGB-Values but the difference is really small (rounding error).
Resulting Screenshot:
![enter image description here][1]
Thanks @someonewithpc! [1]: https://i.sstatic.net/JmYdI.png