Only a pie with Legends in Wedges picks its legend labels' fill, white on
dark wedges. Paint visits and swatch mappings now leave its default black
legend fill out only for such a pie; other graphs draw the kept fill, so
it is visited and mapped like the other label fills. A color mode change
still leaves the default black legend fill as the default, so turning on
Legends in Wedges later keeps the white labels on dark wedges.