Need a sample / feature palette for the proportion_plots

[mortonjt]

Here is the function signature for the proportion_plots

    """ Plot the mean proportions of features within a balance.

    This plots the numerator and denominator components within a balance.

    Parameters
    ----------
    table : pd.DataFrame
       Table of relative abundances.
    metadata : pd.DataFrame
       Samples metadata
    feature_metadata : pd.DataFrame
       The metadata associated to the features.
    category : str
       Name of sample metadata category.
    left_group : str
       Name of group within sample metadata category to plot
       on the left of the plot.
    right_group : str
       Name of group within sample metadata category to plot
       on the right of the plot.
    label_col : str
       Column in the feature metadata table to summarize by.
    num_color : str
       Color to plot the numerator.
    denom_color : str
       Color to plot the denominator.

    Returns
    -------
    ax_num : matplotlib.pyplot.Axes
       Matplotlib axes for the numerator bars
    ax_denom : matplotlib.pyplot.Axes
       Matplotlib axes for the denominator bars

We need to keep the feature coloring and sample_coloring separate