plot test failing under MPL 1.1.0
in test_graphics.py

```
    @slow
    def test_time_series_plot_color_with_empty_kwargs(self):
        import matplotlib.pyplot as plt

        plt.close('all')
        for i in range(3):
            ax = Series(np.arange(12) + 1, index=date_range(
            '1/1/2000', periods=12)).plot()

        line_colors = [ l.get_color() for l in ax.get_lines() ]
        self.assert_(line_colors == ['b', 'g', 'r'])
```

fails because line_colors are returned as hex (MPL 1.1.0)

Can anyone confirm?
