add color_list attribute so it gets kwargs

If I have this right you can add a customise color list as per you code.  It just needs to init using the supplied value.

I was wondering if there is a way of getting the used color values when you  use a built in like category20c.  The use case, I would like to create a pie chart and use category20c (say 15 items) and THEN use the resulting colors for a pie chart (say 200 items) which is classified as per the pie chart.  Hope this makes sense.