I personally haven't seen it with my files either....when I removed the color info it went away.... But it's crazy to me most of the HEVC MKV files I have.... the color information is blank across the board....and those files play fine... What is the POINT of this color information being in some MKV files when they play fine without it? I noticed a series I encoded using Handbrake HEVC 720p preset... it must have PUT the color information there because those files were NOT blank... I wish I could just right click over color information in the header editor and remove all color information instead of going down through each one individually.... it's a total pain....
If you read the MKV specification, you will see that the color info and color mastering info are totally optional. They are MKV metadata that can be used in any way the programmer wants to categorize the file, but they are not needed by the player for accurate playback.
Both Handbrake and ffmpeg fill out those headers in an effort to be good, polite citizens. I think Roku is attempting to use the info to configure their video upscaler, but whatever they are doing is just incorrect.
