Do to licensing Dobly Vision cannot be transcoded by Plex Media Server which means it must be direct playable on client. Which is why tonemapping (which fixes the muted colors) DV will not work as it is the transcoder that does that.
Most devices if they support Dolby Vision only support the streaming profile, which is profile 5 if I recall. The TV, Receiver, HDMI cables and any other devices in chain must support as well.
There is info here specific to Roku support. Roku DV Support
