Setting the tv to 4.4.4 passthrough slightly helped for me, it still has no blue when i turn the PC on, but when i go into windows display settings to turn dolby video on and off again, it fixes it, (don't have to do anything or click anything in the display settings, just the act of opening the windows display settings gives me the blue back.
However if I alt tab out of a game that is using auto HDR back into a normal windows program it kills the blue channel again and I have to do switch on and off dolby vision as before.