def change_font_color(font_color = '000000')
      validate_worksheet
      Color.validate_color(font_color)

      font = get_cell_font.dup
      font.set_rgb_color(font_color)
      update_font_references(font)
    end
def change_font_color(font_color = '000000')
      validate_worksheet
      Color.validate_color(font_color)

      font = get_cell_font.dup
      font.set_rgb_color(font_color)
      update_font_references(font)
    end
Changes font color of cell