ΔE 22.1, loose: different enough that you should pick on purpose. Transparent Brown Iron Oxide is a little darker, much more saturated than Bullwhack Brown.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Transparent Brown Iron Oxide is a little darker, much more saturated than Bullwhack Brown.
The same difference applies the other way round: Bullwhack Brown is a little lighter, much more muted.
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 Bullwhack Brown on the colour wheel See Transparent Brown Iron Oxide on the colour wheel
All matches: Bullwhack Brown equivalents · Transparent Brown Iron Oxide equivalents