MPC-HC subtitles secondary color, what is it for?

[Perplexer]

I need some help with the subtitles option in Media Player Classic Homecinema.

Under "Options -> Subtitles -> Default Style -> Colors & Transparency" I can see and set the "Primary" and "Secondary" colors. The subtitles that are displayed are always white for me, meaning they use the "Primary" color. The question I have is: when does the "Secondary" color come into play? How can I get subtitles to display in that green color?

Thank's in advance for clarification.

[Subtitles]

I am not familiar with this software.
I use SubtitleEdit to create subtitle files of any type but mostly *.srt
The advantages of different colours is to distinguish multispeakers names by their colours.
Using SubtitleEdit, let us say you want to colour the text "Hello World" in Yellow.
Selct the subtitle line and using mouse > Right Click > Color and choose Yellow then click OK. You will get
<font color="#fffc00">Hello World</font>

If you go to Settings > Appearance you can select the default font colour and background.
I am guessing in your case, the secondary colour is probably the background.
It is weird that the text is always white. You should be able to select any font colour you want for text.

[Perplexer]

The font is white because I have the "Primary" color set to white. I can change that color and the subtitles will then be a different color. The "Outline" and "Shadow" colors will also reflect on the subtitles (after a program restart). So these three I can change and see the effect on the subtitles, no problem. But I can never get that "Secondary" (green) color to show up in any subtitle. That's why I would like to know what it is for; when does it take effect on a subtitle?

[zing269]

It is used in karaoke effects in .ass subtitles.

\k: Before highlight, the syllable is filled with the secondary color and alpha. When the syllable starts, the fill is instantly changed to use primary color and alpha.

[Subtitles]

It is used in karaoke effects in .ass subtitles.

\k: Before highlight, the syllable is filled with the secondary color and alpha. When the syllable starts, the fill is instantly changed to use primary color and alpha.

Exactly.
This link also mentions it is used for karoake
http://kyotaegisub.weebly.com/typesetting-basics.html