Curious. It renders the subtitles for me just like it does with vo=gpu.
After you exited, the output should remain, did mpv load the subtitles like in your screenshot above?
Might be worth looking into, but that is an area outside my experience.
No, I didn’t see any subtitles and then when I dragged and drop the file .srt the subtitles didn’t appear in this case
I tried with Haruna like @Ben said and same result:
You can manually load it with --sub-file=subpath.
Now yes, with this command added the subtitles but same colors 
:(.
It’s very weird. Thanks for continue trying with me!
Does this happen with any video or just this one?
So not some fringe colorspace issue either.
The rest of the video renders correctly, so nothing there either.
I am out of ideas.
The color itself is 7f7f7f, you could try grepping it in .config, in case its not computed to maybe find something.
If its really affecting all applications similarly, despite configuration, and you have also tried clearing those settings/cache … then
I might wonder about some other random stuff like … gfx or compositor?
neofetch and the like are not very good system info tools.
Please show
inxi -Fazy
Some html formatting tags can be used in subrip, including font tags which can specify a colour. They work in at least mpv, vlc and smplayer.
So, have you opened the .srt in a text editor to check?
Just in case, here’s a quick script to remove font tags. It will create a new file by replacing .srt with .unfont.srt, otherwise the name and path will be the same as the original.
#!/usr/bin/bash
# DESC: Remove font tags from .srt files, $1 = /path/to/file.srt
name="${1%.srt}.unfont.srt"
sed -e 's/<\/font>//g' -e 's/<font .*>//g' < "$1" > "$name"