GUI: read color information from track metadata of Matroska files
GUI users may be curious about the recently added "color information" input fields, and drag several files into the GUI to check their values.
The GUI doesn't seem to fill these fields with metadata from a Matroska file, although it does preserve the values when copying such a video track.
Color information of video track when added as source in the muxer GUI:
mkvmerge-produced MKV (all fields preserved):
Note that MKVToolNix uses US & UK spelling mixedly when talking about color/colour.
You may want to add a tiny PO file with affected strings, if you have no plan to change the "colour" preference of the 2016 contributor (most Chinese students were educated with books co-authored with British or Canadian teams).