title: How to apply pyqtgraph.mkPen() to a GridItem?
body: <p>does anybody know how to apply pyqtgraph.mkPen() to a gridItem. In the following example the pen works for a PlotCurveItem but I was not able to make it work for the grid.</p>
  
  <pre><code>import pyqtgraph as pg
  from pyqtgraph.Qt import QtCore, QtGui
  import numpy as np
  
  #sample data
  x = np.arange(0,1,0.1)
  y = [0,0,0,2,2,8,9,2,0,0]
  
  
  # mkPen for curve
  curvePen = pg.mkPen(color=(255, 15, 10), style=QtCore.Qt.DotLine)
  
  # plot the curve
  plt = pg.plot()
  curve = pg.PlotCurveItem(x,y[:-1],pen=curvePen,stepMode=True)
  plt.addItem(curve)
  
  
  # mkPen for grid
  gridPen = pg.mkPen(color=(200, 200, 255), style=QtCore.Qt.DotLine)
  
  # How do I apply this gridPen to the following grid
  
  # define grid
  plt_grid = pg.GridItem()
  plt.addItem(plt_grid)
  
  plt.show()
  
  
  if __name__ == '__main__':
      import sys
      if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
          QtGui.QApplication.instance().exec_()
  </code></pre>
  
  <p>Thanks a lot 
  Regards
  Michael</p>