diff --git a/openmc/plotter.py b/openmc/plotter.py
index 9e356b1eda..488de56d87 100644
--- a/openmc/plotter.py
+++ b/openmc/plotter.py
@@ -3,6 +3,7 @@ from six import string_types
 from itertools import chain
 
 import numpy as np
+import matplotlib.pyplot as plt
 
 import openmc.checkvalue as cv
 import openmc.data
@@ -121,9 +122,6 @@ def plot_xs(this, types, divisor_types=None, temperature=294., axis=None,
         generated.
 
     """
-
-    from matplotlib import pyplot as plt
-
     cv.check_type("plot_CE", plot_CE, bool)
 
     if isinstance(this, openmc.Nuclide):
diff --git a/openmc/universe.py b/openmc/universe.py
index 952f61dac1..718825db97 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -1,3 +1,4 @@
+from copy import copy
 from collections import OrderedDict, Iterable
 from numbers import Integral, Real
 import random
@@ -5,6 +6,8 @@ import sys
 
 from six import string_types
 import numpy as np
+import matplotlib.pyplot as plt
+from matplotlib.colors import to_rgba
 
 import openmc
 import openmc.checkvalue as cv
@@ -234,9 +237,9 @@ class Universe(object):
             Indicate whether the plot should be colored by cell or by material
         colors : dict
             Assigns colors to specific materials or cells. Keys are instances of
-            :class:`Cell` or :class:`Material` and values are RGB 3-tuples or
-            RGBA 4-tuples. Red, green, blue, and alpha should all be floats in
-            the range [0.0, 1.0], for example:
+            :class:`Cell` or :class:`Material` and values are RGB 3-tuples, RGBA
+            4-tuples, or strings indicating SVG color names. Red, green, blue,
+            and alpha should all be floats in the range [0.0, 1.0], for example:
 
             .. code-block:: python
 
@@ -256,8 +259,6 @@ class Universe(object):
             :func:`matplotlib.pyplot.imshow`.
 
         """
-        import matplotlib.pyplot as plt
-
         # Seed the random number generator
         if seed is not None:
             random.seed(seed)
@@ -267,9 +268,9 @@ class Universe(object):
             colors = {}
         else:
             # Convert to RGBA if necessary
-            for obj, rgb in colors.items():
-                if len(rgb) == 3:
-                    colors[obj] = rgb + (1.0,)
+            colors = copy(colors)
+            for obj, color in colors.items():
+                colors[obj] = to_rgba(color)
 
         if basis == 'xy':
             x_min = center[0] - 0.5*width[0]
@@ -325,7 +326,8 @@ class Universe(object):
                     img[j, i, :] = colors[obj]
 
         # Display image
-        plt.imshow(img, extent=(x_min, x_max, y_min, y_max), **kwargs)
+        plt.imshow(img, extent=(x_min, x_max, y_min, y_max),
+                   interpolation='nearest', **kwargs)
 
         # Show or save the plot
         if filename is None:
diff --git a/tests/test_triso/inputs_true.dat b/tests/test_triso/inputs_true.dat
index 43b15b037c..12dd4e7a64 100644
--- a/tests/test_triso/inputs_true.dat
+++ b/tests/test_triso/inputs_true.dat
@@ -442,7 +442,7 @@
 </settings>
 <?xml version="1.0"?>
 <plots>
-  <plot id="1" type="slice" basis="xy" color="material"
+  <plot id="1" type="slice" basis="xy" color_by="material"
     origin="0.0 0.0 0.0" width="1.0 1.0" pixels="400 400">
   </plot>
 </plots>