ΔE 10.7, fair: the same colour family, but not a straight swap. Black Skintone is a little lighter, more saturated, cooler than Bootstrap Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Black Skintone is a little lighter, more saturated, cooler than Bootstrap Brown.
The same difference applies the other way round: Bootstrap Brown is a little darker, more muted, warmer.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Bootstrap Brown on the colour wheel See Black Skintone on the colour wheel
All matches: Bootstrap Brown equivalents · Black Skintone equivalents