SetUnderlineColor
CharacterStyleDataRef data = fStyleData->SetUnderlineColor(which);
CharacterStyleDataRef data = fStyleData->SetUnderlineColor(color);
bool SetUnderlineColor(color_which which);
bool SetUnderlineColor(rgb_color color);
CharacterStyleDataRef SetUnderlineColor(color_which which);
CharacterStyleDataRef SetUnderlineColor(rgb_color color);