code: func (s Style) Foreground(c Color) Style {
  	if c == ColorDefault {
  		return (s &^ (0x1ffffff00000000 | styleFgSet))
  	}
  	return (s &^ Style(0x1ffffff00000000)) |
  		((Style(c) & 0x1ffffff) << 32) | styleFgSet
  }
docs: // Foreground returns a new style based on s, with the foreground color set
  // as requested.  ColorDefault can be used to select the global default.