Is there any way to get the '%' in the BarLegend to be black instead of light gray?

ContourPlot[x^2 + y^2, {x, -10, 10}, {y, -10, 10}, 
PlotLegends -> BarLegend[Automatic, LegendFunction -> "Panel",
   LabelStyle -> {FontFamily -> "Monaco", FontSize -> 18, 
   FontColor -> Black}],
FrameStyle -> Black,
TargetUnits -> "%"]