diff --git a/csa/elementary.py b/csa/elementary.py
index 4d848b8..f3c5d2a 100644
--- a/csa/elementary.py
+++ b/csa/elementary.py
@@ -71,6 +71,22 @@ def ival (beg, end):
 # Cartesian product
 #
 def cross (set0, set1):
+    """
+    Compute the Cartesian product of two sets.
+
+    Note
+    ----
+    The Cartesian product returned by `cross()` is not automatically
+    restricted to a finite mask. When visualized using `show()`,
+    connections may appear in the default (infinite) mask unless
+    explicitly multiplied with a finite mask.
+
+    Example
+    -------
+    # To obtain a bounded all-to-all connectivity pattern:
+    cross(A, B) * full(len(A), len(B))
+    """
+
     return _cs.intervalSetMask (set0, set1)
 
 # Elementary masks
diff --git a/csa/plot.py b/csa/plot.py
index dd2fecc..c6a6ced 100644
--- a/csa/plot.py
+++ b/csa/plot.py
@@ -19,6 +19,14 @@
 import numpy as _numpy
 import matplotlib
 import matplotlib.pyplot as _plt
+from matplotlib.colors import ListedColormap
+
+# Color mapping for masks in show()
+MASK_COLOR = {
+    'full': 'purple',
+    'oneToOne': 'purple',
+    'randomMask': 'green',
+}
 
 from . import elementary
 
@@ -40,9 +48,15 @@ def show (cset, N0 = 30, N1 = None):
     N1 = N0 if N1 == None else N1
     _plt.clf ()
     _plt.axis ('equal')
+    # Determine color from mask type
+    mask_tag = getattr(cset, 'tag', None)
+    color = MASK_COLOR.get(mask_tag, 'gray')
+    # Create a colormap with only this color
+    cmap = ListedColormap([color_name])
     a = _numpy.zeros ((N0, N1))
     for (i, j) in elementary.cross (range (N0), range (N1)) * cset:
         a[i,j] += 1.0
+    # Show with consistent color
     _plt.imshow (a, interpolation='nearest', vmin = 0.0, vmax = 1.0)
     _plt.show ()