Order of colours/categories in Vizlib stacked barchart

I made the following graph in VizLib (the top one) and it looks very good but the order of the colours/categories is inconsistent. I always want the dark blue at the bottom and the light blue at the top for example. In regular QlikSense graphs this works as expected so I am using those now, but they look less nice, especially the legend. Is this a bug in VizLib and if so, can it be fixed?