Serie color has different behavior along different paths...
Created originally on Bitbucket by Anonymous
In instances of openpyxl.chart.Serie, if I set the color by using the color property the setter calls short_color() on the provided color before setting it. If I pass the color in via the Serie constructor, the color is set "as is" without being passed through short_color(). This latter seems to cause problems with Excel 2007.
I suggest that the constructor setter should also call short_color() on the input.