Preview Vapoursynth script with MPV

[belonesox]

I wish to preview vapoursynth scripts with MPV,
ideally with seeking, but I still cannot align MPV with VS on formats/colors, etc.

Consider small project:
https://github.com/belonesox/wtf-vap...th-mpv-preview

release.py:

#!/usr/bin/env python3
import vapoursynth as vs

core = vs.get_core()
video = core.std.BlankClip(format=vs.YUV420P10, length=1000, color=[128, 190, 128]) 
video = core.sub.Subtitle(video, "WTF???", 0, 500, style="sans-serif,200,&H00FF00FF")
video.set_output()

When I build it with 'build.sh'

vspipe --y4m release.py - | ffmpeg -i pipe: encoded.mkv

— all OK

When I preview it with 'preview-ffplay.sh'

vspipe --y4m release.py - | ffplay -i pipe:

— all OK

But how I can preview it with MPV?

I tried

vspipe --y4m release.py - |  mpv --demuxer rawvideo --demuxer-rawvideo-mp-format=yuv420p10 -

and tried all formats supported by MPV...
but still getting wrong result ("moving text with wrong color").

What am I doing wrong?