Hi jd17!
OMG! You are right!!
It's an 8bit source.
Tried a bit around and compared it against a main 8bit encoding and the problem was gone. (Using StaxRip's comparison tool)
I then opened the 8bit and the main10 10bit file in VLC and... again no washed out colors.
So the issue seems to be related to StaxRip's screen comparison tool.
Thx a lot, Sherlock!