[brazen1]

I don't use a Shield or Plex.  Can't help you with that.  For a PC I use GPU RGB Full and match that 0-255 on my display.  In Kodi, I leave 16-235 unchecked so it too uses 0-255 matching my entire chain.  Your Shield (may) be using YCbCr at 16-235 limited and your display is also set to 16-235 limited.  Then when you switch to PC instead of Shield, PC is probably set to 0-255 Full while display is still set to 16-235 Limited and you have a mismatch?  PC prefers setting to RGB while all other devices prefer setting to YCbCr.  I know there are various combinations of full and limited as well as automatic switching depending on the source.  I can't help you with that because I only use the one.  Try setting your display to auto and see if it auto switches (if) your Shield and your PC use different color spaces.  Also, from your pics, I'm not certain it's a color space issue but it looks like it could be.  I doubt 8bit vs 10/12bit would be that dramatic.