Maybe it is not a bug, but i consider this as a bug :)
I would suppose, that if I define a DrawingSupplier, then one color will be associated with each data item. This is not the case, as my example shows. See the code and the picture. It seems, that if one data item "does not paint anything" (including legend or text), then the color is not taken for it.
My humble guess is that not only pie chart is affected by this bug.