Blackert Brown vs Tan

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Tan is more saturated, cooler than Blackert Brown.

Can I use Tan instead of Blackert Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Tan is more saturated, cooler than Blackert Brown.

Can I use Blackert Brown instead of Tan?

The same difference applies the other way round: Blackert Brown is 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.