I can't choose the color of the strikethrough line, it automatically sets the same color as the font.
BTW: The ODF file format hasn't any text property for the color for the line. Moreover I wanrt to mention https://bugs.freedesktop.org/show_bug.cgi?id=53412 which includes Apple's RTF extensions containing the same feature for RTF. (so whoever want to work on this and proposing a new property at OASIS can argue with compatibility with RTF/RTFD by Apple. Don't know if Pages contains this feature. I have to look up that fact)
Haven't got the resource capacity to implement this.