code: func WmColormapWindowsSet(xu *xgbutil.XUtil, win xproto.Window,
  	windows []xproto.Window) error {
  
  	return xprop.ChangeProp32(xu, win, "WM_COLORMAP_WINDOWS", "WINDOW",
  		xprop.WindowToInt(windows)...)
  }
docs: // WM_COLORMAP_WINDOWS set