[Connect C++] IElementGraphicsProcessor & Text color

I used IElementGraphicsProcessor to do text tessellation, one issue I find given above example, the tessellated text facet color seems confusing and the text's color can't be get:
in details for each text facet:
    m_fillColor = displayParams.GetFillColor(); // always return INVALID_COLOR
    m_lineColor = displayParams.GetLineColor(); // always return text background border color

For text facet I supposed should use the fill color? The fill color is INVALID so I don't know how to get the correct fill color. And the line color is always the border color which is not correct either.

Thanks,

Danny