BUG: set default edgecolor to none and fix facecolor

Author: alexandercbooth

pandas/tools/plotting.py

@@ -361,10 +361,14 @@ def scatter_matrix(frame, alpha=0.5, figsize=None, ax=None, grid=False,
 
     # workaround because `c='b'` is hardcoded in matplotlibs scatter method
     # only set default for `c` if `color` kwarg not supplied
+    # edgecolors default required otherwise `color` has a border
     # GH 14855
+    kwds.setdefault('edgecolors', 'none')
     if 'color' in kwds:
         pass
-    else:
+    if 'facecolor' in kwds:
+        kwds.setdefault('facecolor', plt.rcParams['patch.facecolor'])
+    if 'c' in kwds:
         kwds.setdefault('c', plt.rcParams['patch.facecolor'])
 
     boundaries_list = []