Black Brown vs Gal Vorbak Red

How close are they?

ΔE 15.9, loose: different enough that you should pick on purpose. Gal Vorbak Red is a little lighter, much more saturated than Black Brown.

Can I use Gal Vorbak Red instead of Black Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Gal Vorbak Red is a little lighter, much more saturated than Black Brown.

Can I use Black Brown instead of Gal Vorbak Red?

The same difference applies the other way round: Black Brown is a little darker, 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.