I had a Samsung NU7100 TV. It was a pain to calibrate it for HDR input signal.
The colors did indeed look dull and washed out. The settings that helped to fix this are Contrast Enhancer - it should be enabled (try Low or High) and Gamma ST.2084 (try 1,2 or 3).
My other settings as far as I remember were:
Picture Mode: Movie
Brightness: 5 (at max)
Contrast: 45
Colour: 25