Update lib/matplotlib/colors.py

Co-authored-by: Greg Lucas <[email protected]>

Author: timhoffm

lib/matplotlib/colors.py

@@ -1228,10 +1228,7 @@ def monochrome(self):
         if not self._isinit:
             self._init()
 
-        N = len(self._lut) - 3  # disregard over / under / bad
-        if N <= 1:
-            return True
-        return np.all(self._lut[0] == self._lut[1:N])
+        return self.N <=1 or np.all(self._lut[0] == self._lut[1:self.N])
 
     def resampled(self, lutsize):
         """Return a new colormap with *lutsize* entries."""