Subtitle color

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Hi there,
This is maybe a stupid question but I am using the PS3 Media Server 1.50.0 on my Mac.
I want to change the subtitle color of a .mkv file. According to VLC it's got ASS/SRT subtitles but the transcode MEncoder option (Subtitle color) does not work. I tried disableling the "Use ASS Standard Style" option and restarting the server/ps3.

Could somebody tell me what I am missing?