code: func (t *Terminfo) TColor(fi, bi int) string {
  	rv := ""
  	// As a special case, we map bright colors to lower versions if the
  	// color table only holds 8.  For the remaining 240 colors, the user
  	// is out of luck.  Someday we could create a mapping table, but its
  	// not worth it.
  	if t.Colors == 8 {
  		if fi > 7 && fi < 16 {
  			fi -= 8
  		}
  		if bi > 7 && bi < 16 {
  			bi -= 8
  		}
  	}
  	if t.Colors > fi && fi >= 0 {
  		rv += t.TParm(t.SetFg, fi)
  	}
  	if t.Colors > bi && bi >= 0 {
  		rv += t.TParm(t.SetBg, bi)
  	}
  	return rv
  }
docs: // TColor returns a string corresponding to the given foreground and background
  // colors.  Either fg or bg can be set to -1 to elide.