[WeldSpark]

So confirming you have the SDR (Rec.709) color conversion > TV display issue when the Shield is set to 4K 59.940Hz YUV420 10-bit Rec.2020
As displayed in the top picture in @hdmkv's post HERE ?

NVIDIA need to implement colorspace switching, and that needs to be done at the Linux Kernel / driver level, independant of Google's OS.
Like all the other Android chipset vendors have already done.

I will be very surprised if that ends up being a quick fix. A whole bunch of testing needs to be done as well. 

Thanks for pitching in. No I used the wrong terminology. It's not washed out, comparing to the pictures you linked to.

The picture on the Shield, especially in Kodi seems darker. In android tv the colors seem oversaturated. I'm not a tv calibration expert, but somethings feels off.

I use the same TV image settings that I use on Odroid c2, it's recommended settings from rtings.com, they have worked satisfactory on my Odroid.

I can only compare to my Odroid c2. I hope you can understand what I mean, it's hard to explain.

I use 1080p in Nvidia shield, because most of my content is 1080p. The inbuilt scaling from 1080 to 4k was quite bad. But I guess in Kodi it will change resolution depending on the source.

Just found out something, when I manually change color color spaces on the TV settings (or what it's called) it gets better. sRGB/BT.709 is better, when I switch to BT.2020 it gets over saturated.

In other words, if I want to watch HDR content I need to manually switch color space? 

 Ideally your TV colour space should be left on Auto ?  That means it should match the gamut of the source device - switching between 709 when fed 709 video and 2020 when fed 2020 video.  If you have a device that automatically gamut switches between 709 and 2020 HDMI output, or your TV has an HDMI input fed from an AVR that has both 709 and 2020 sources, then it should switch accordingly.  I'd avoiding forcing a specific colour space unless you absolutely have to.

The Shield TV should output either Rec 2020 OR Rec 709 - but will be fixed in one or the other outputs, and won't switch colour gamut/space output dynamically.  Instead it will do an internal conversion between the two.   If you have a Rec 2020 HDR display then the advice is usually to run the Shield TV in YUV 12 bit 4:2:2 Rec 2020 if you can.  The Shield TV will then map Rec 709 gamut content into the Rec 2020 colour gamut, staying in SDR (standard dynamic range) using an approved method.  Where this CAN be an issue is that some TVs don't display Rec 2020 SDR as the Shield TV expects them too...  In this case manually switching the output of the Shield TV to a Rec 709 gamut output may deliver better results when watching Rec 709 content (which will be SDR in almost every case)   Similarly all HDR content in the wild is likely to be Rec 2020 colour gamut, so you'd then need to switch the Shield TV back to a Rec 2020 gamut output when watching HDR content.

If I leave the TV settings in auto the colors will be distorted, I need to manually change to 709 so make it look alright. It won't change correctly on auto. So I manually need to change this I guess, it feels quite bad.