Is there a function to return all single letter colors in Matplotlib?

The built in colors are available via matplotlib.colors.ColorConverter.colors

>>> print(matplotlib.colors.ColorConverter.colors)
{u'b': (0.0, 0.0, 1.0),
 u'c': (0.0, 0.75, 0.75),
 u'g': (0.0, 0.5, 0.0),
 u'k': (0.0, 0.0, 0.0),
 u'm': (0.75, 0, 0.75),
 u'r': (1.0, 0.0, 0.0),
 u'w': (1.0, 1.0, 1.0),
 u'y': (0.75, 0.75, 0)}

It seems that the @Andy's answer returns all available colors with varying color names.

to get single color letters only you can use the following:

 >>> [x for x in matplotlib.colors.ColorConverter.colors.keys() if len(x)==1]