title: set rgba color of points in matplotlib
body: <p>According to the docs this is supposed to work. It does not. I must be misreading the docs. Anybody have the fix?</p>
  
  <pre><code>from pylab import *
  N = 100
  x = randn(N)
  y = randn(N)
  c = rand(N, 4)
  plot(x, y, 'o', c=c)
  </code></pre>
  
  <p>Error in IPython notebook (python3):</p>
  
  <pre><code>lib/python3.3/site-packages/IPython/core/formatters.py:239: FormatterWarning: Exception in image/png formatter: to_rgba: Invalid rgba arg "[[ 0.29844256  0.96853857  0.75812229  0.22794978]
   [ 0.81606887  0.31641358  0.53254456  0.44198844]
   [ 0.06961026  0.3265891   0.03006253  0.00485412]
   [ 0.32580911  0.86645991  0.04140443  0.35550554]
  </code></pre>
  
  <p>Error in plain IPython (python3):</p>
  
  <pre><code>ValueError: to_rgba: Invalid rgba arg "[[ -2.78401664e-01  -8.33924015e-01   7.54508871e-01]
   [ -3.02839674e-01  -1.18292516e+00  -7.71274654e-01]
   [ -3.58099013e-01  -1.18899472e+00   1.39868995e+00]
  </code></pre>
  
  <p>Docs:</p>
  
  <pre><code>help(plot)
  
  ....
  
  In addition, you can specify colors in many weird and
  wonderful ways, including full names (``'green'``), hex
  strings (``'#008000'``), RGB or RGBA tuples (``(0,1,0,1)``) or
  grayscale intensities as a string (``'0.8'``).  Of these, the
  string specifications can be used in place of a ``fmt`` group,
  but the tuple forms can be used only as ``kwargs``.
  </code></pre>