code: def lasso_leftdown(self, event=None):
          
          try:
              self.report_leftdown(event=event)
          except:
              return
  
          if event.inaxes:
              # set lasso color
              color='goldenrod'
              cmap = getattr(self.conf, 'cmap', None)
              if isinstance(cmap, dict):
                  cmap = cmap['int']
              try:
                  if cmap is not None:
                      rgb = (int(i*255)^255 for i in cmap._lut[0][:3])
                      color = '#%02x%02x%02x' % tuple(rgb)
              except:
                  pass
              self.lasso = Lasso(event.inaxes, (event.xdata, event.ydata),
                                 self.lassoHandler)
              self.lasso.line.set_color(color)
docs: leftdown event handler for lasso mode