<p dir="auto">I hope I'm not reporting an issue that's already known. Starting with matplotlib==2.0.0b1, pyplot.bar does not cycle through colors anymore. Instead, if I pass list of colors, it only uses color 'C0'.</p>
<p dir="auto">Minimum code to reproduce bug:</p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt
x_pos = [0, 1, 2]
heights = [1, 2, 3]
colors = ['0.2', '0.5', '0.8']
print('Works properly:')
[plt.bar(left=x_pos[ii], height=heights[ii], color=colors[ii]) for ii in range(len(x_pos))]
plt.show()
print('Does not work aynmore:')
plt.bar(left=x_pos, height=heights, color=colors)
plt.show()"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>
<span class="pl-s1">x_pos</span> <span class="pl-c1">=</span> [<span class="pl-c1">0</span>, <span class="pl-c1">1</span>, <span class="pl-c1">2</span>]
<span class="pl-s1">heights</span> <span class="pl-c1">=</span> [<span class="pl-c1">1</span>, <span class="pl-c1">2</span>, <span class="pl-c1">3</span>]
<span class="pl-s1">colors</span> <span class="pl-c1">=</span> [<span class="pl-s">'0.2'</span>, <span class="pl-s">'0.5'</span>, <span class="pl-s">'0.8'</span>]
<span class="pl-en">print</span>(<span class="pl-s">'Works properly:'</span>)
[<span class="pl-s1">plt</span>.<span class="pl-en">bar</span>(<span class="pl-s1">left</span><span class="pl-c1">=</span><span class="pl-s1">x_pos</span>[<span class="pl-s1">ii</span>], <span class="pl-s1">height</span><span class="pl-c1">=</span><span class="pl-s1">heights</span>[<span class="pl-s1">ii</span>], <span class="pl-s1">color</span><span class="pl-c1">=</span><span class="pl-s1">colors</span>[<span class="pl-s1">ii</span>]) <span class="pl-k">for</span> <span class="pl-s1">ii</span> <span class="pl-c1">in</span> <span class="pl-en">range</span>(<span class="pl-en">len</span>(<span class="pl-s1">x_pos</span>))]
<span class="pl-s1">plt</span>.<span class="pl-en">show</span>()
<span class="pl-en">print</span>(<span class="pl-s">'Does not work aynmore:'</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">bar</span>(<span class="pl-s1">left</span><span class="pl-c1">=</span><span class="pl-s1">x_pos</span>, <span class="pl-s1">height</span><span class="pl-c1">=</span><span class="pl-s1">heights</span>, <span class="pl-s1">color</span><span class="pl-c1">=</span><span class="pl-s1">colors</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">show</span>()</pre></div>
<p dir="auto">Output:</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://cloud.githubusercontent.com/assets/20988354/22149638/2e2c2d96-df15-11e6-8759-8e95506a2ac8.png"><img width="382" alt="img" src="https://cloud.githubusercontent.com/assets/20988354/22149638/2e2c2d96-df15-11e6-8759-8e95506a2ac8.png" style="max-width: 100%;"></a></p>
<p dir="auto">Here's the output using the same code with matplotlib==1.5.3</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://cloud.githubusercontent.com/assets/20988354/22149823/42868696-df16-11e6-9641-57a29968a766.png"><img width="446" alt="img2" src="https://cloud.githubusercontent.com/assets/20988354/22149823/42868696-df16-11e6-9641-57a29968a766.png" style="max-width: 100%;"></a></p>
<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>

<p dir="auto">pyplot.plot worked fine (including version 2.0.0) with the Qt4/PySide backend specified in matplotlibrc. With version 2.0.1, it seems to try to use Qt5 instead and fails.</p>
<p dir="auto"><strong>Code for reproduction</strong></p>

<p dir="auto">Any code</p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt

plt.plot([1, 2, 3])
plt.show()"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>

<span class="pl-s1">plt</span>.<span class="pl-en">plot</span>([<span class="pl-c1">1</span>, <span class="pl-c1">2</span>, <span class="pl-c1">3</span>])
<span class="pl-s1">plt</span>.<span class="pl-en">show</span>()</pre></div>
<p dir="auto"><strong>Actual outcome</strong></p>

<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="c:\python34\lib\site-packages\matplotlib\pyplot.py in plot(*args, **kwargs)
   3304 @_autogen_docstring(Axes.plot)
   3305 def plot(*args, **kwargs):
-&gt; 3306     ax = gca()
   3307     # Deprecated: allow callers to override the hold state
   3308     # by passing hold=True|False

c:\python34\lib\site-packages\matplotlib\pyplot.py in gca(**kwargs)
    948     matplotlib.figure.Figure.gca : The figure's gca method.
    949     &quot;&quot;&quot;
--&gt; 950     return gcf().gca(**kwargs)
    951
    952 # More ways of creating axes:

c:\python34\lib\site-packages\matplotlib\pyplot.py in gcf()
    584         return figManager.canvas.figure
    585     else:
--&gt; 586         return figure()
    587
    588

c:\python34\lib\site-packages\matplotlib\pyplot.py in figure(num, figsize, dpi, facecolor, edgecolor, frameon, FigureClass, **kwargs)
    533                                         frameon=frameon,
    534                                         FigureClass=FigureClass,
--&gt; 535                                         **kwargs)
    536
    537         if figLabel:

c:\python34\lib\site-packages\matplotlib\backends\backend_qt4agg.py in new_figure_manager(num, *args, **kwargs)
     44     FigureClass = kwargs.pop('FigureClass', Figure)
     45     thisFig = FigureClass(*args, **kwargs)
---&gt; 46     return new_figure_manager_given_figure(num, thisFig)
     47
     48

c:\python34\lib\site-packages\matplotlib\backends\backend_qt4agg.py in new_figure_manager_given_figure(num, figure)
     52     &quot;&quot;&quot;
     53     canvas = FigureCanvasQTAgg(figure)
---&gt; 54     return FigureManagerQT(canvas, num)
     55
     56

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in __init__(self, canvas, num)
    486         self.window.statusBar().addWidget(self.statusbar_label)
    487
--&gt; 488         self.toolbar = self._get_toolbar(self.canvas, self.window)
    489         if self.toolbar is not None:
    490             self.window.addToolBar(self.toolbar)

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _get_toolbar(self, canvas, parent)
    537         # attrs are set
    538         if matplotlib.rcParams['toolbar'] == 'toolbar2':
--&gt; 539             toolbar = NavigationToolbar2QT(canvas, parent, False)
    540         else:
    541             toolbar = None

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in __init__(self, canvas, parent, coordinates)
    583
    584         QtWidgets.QToolBar.__init__(self, parent)
--&gt; 585         NavigationToolbar2.__init__(self, canvas)
    586
    587     def _icon(self, name):

c:\python34\lib\site-packages\matplotlib\backend_bases.py in __init__(self, canvas)
   2758         self._active = None
   2759         self._lastCursor = None
-&gt; 2760         self._init_toolbar()
   2761         self._idDrag = self.canvas.mpl_connect(
   2762             'motion_notify_event', self.mouse_move)

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _init_toolbar(self)
    599                 self.addSeparator()
    600             else:
--&gt; 601                 a = self.addAction(self._icon(image_file + '.png'),
    602                                    text, getattr(self, callback))
    603                 self._actions[callback] = a

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _icon(self,name)
    589             name = name.replace('.png', '_large.png')
    590         pm = QtGui.QPixmap(os.path.join(self.basedir, name))
--&gt; 591         pm.setDevicePixelRatio(self.canvas._dpi_ratio)
    592         return QtGui.QIcon(pm)
    593

AttributeError: 'PySide.QtGui.QPixmap' object has no attribute 'setDevicePixelRatio'"><pre class="notranslate"><code class="notranslate">c:\python34\lib\site-packages\matplotlib\pyplot.py in plot(*args, **kwargs)
   3304 @_autogen_docstring(Axes.plot)
   3305 def plot(*args, **kwargs):
-&gt; 3306     ax = gca()
   3307     # Deprecated: allow callers to override the hold state
   3308     # by passing hold=True|False

c:\python34\lib\site-packages\matplotlib\pyplot.py in gca(**kwargs)
    948     matplotlib.figure.Figure.gca : The figure's gca method.
    949     """
--&gt; 950     return gcf().gca(**kwargs)
    951
    952 # More ways of creating axes:

c:\python34\lib\site-packages\matplotlib\pyplot.py in gcf()
    584         return figManager.canvas.figure
    585     else:
--&gt; 586         return figure()
    587
    588

c:\python34\lib\site-packages\matplotlib\pyplot.py in figure(num, figsize, dpi, facecolor, edgecolor, frameon, FigureClass, **kwargs)
    533                                         frameon=frameon,
    534                                         FigureClass=FigureClass,
--&gt; 535                                         **kwargs)
    536
    537         if figLabel:

c:\python34\lib\site-packages\matplotlib\backends\backend_qt4agg.py in new_figure_manager(num, *args, **kwargs)
     44     FigureClass = kwargs.pop('FigureClass', Figure)
     45     thisFig = FigureClass(*args, **kwargs)
---&gt; 46     return new_figure_manager_given_figure(num, thisFig)
     47
     48

c:\python34\lib\site-packages\matplotlib\backends\backend_qt4agg.py in new_figure_manager_given_figure(num, figure)
     52     """
     53     canvas = FigureCanvasQTAgg(figure)
---&gt; 54     return FigureManagerQT(canvas, num)
     55
     56

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in __init__(self, canvas, num)
    486         self.window.statusBar().addWidget(self.statusbar_label)
    487
--&gt; 488         self.toolbar = self._get_toolbar(self.canvas, self.window)
    489         if self.toolbar is not None:
    490             self.window.addToolBar(self.toolbar)

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _get_toolbar(self, canvas, parent)
    537         # attrs are set
    538         if matplotlib.rcParams['toolbar'] == 'toolbar2':
--&gt; 539             toolbar = NavigationToolbar2QT(canvas, parent, False)
    540         else:
    541             toolbar = None

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in __init__(self, canvas, parent, coordinates)
    583
    584         QtWidgets.QToolBar.__init__(self, parent)
--&gt; 585         NavigationToolbar2.__init__(self, canvas)
    586
    587     def _icon(self, name):

c:\python34\lib\site-packages\matplotlib\backend_bases.py in __init__(self, canvas)
   2758         self._active = None
   2759         self._lastCursor = None
-&gt; 2760         self._init_toolbar()
   2761         self._idDrag = self.canvas.mpl_connect(
   2762             'motion_notify_event', self.mouse_move)

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _init_toolbar(self)
    599                 self.addSeparator()
    600             else:
--&gt; 601                 a = self.addAction(self._icon(image_file + '.png'),
    602                                    text, getattr(self, callback))
    603                 self._actions[callback] = a

c:\python34\lib\site-packages\matplotlib\backends\backend_qt5.py in _icon(self,name)
    589             name = name.replace('.png', '_large.png')
    590         pm = QtGui.QPixmap(os.path.join(self.basedir, name))
--&gt; 591         pm.setDevicePixelRatio(self.canvas._dpi_ratio)
    592         return QtGui.QIcon(pm)
    593

AttributeError: 'PySide.QtGui.QPixmap' object has no attribute 'setDevicePixelRatio'
</code></pre></div>
<p dir="auto"><strong>Expected outcome</strong></p>


<p dir="auto">Show the plot.</p>
<p dir="auto"><strong>Matplotlib version</strong></p>

<ul dir="auto">
<li>Operating System: Windows 7</li>
<li>Matplotlib Version: 2.0.1</li>
<li>Python Version: 3.4.3</li>
<li>Jupyter Version (if applicable): -</li>
<li>Other Libraries: PySide 1.2.4</li>
</ul>


<p dir="auto">Installed via pip</p>