Khorne Red vs Brown

How close are they?

ΔE 15.5, loose: different enough that you should pick on purpose. Brown is noticeably lighter, more muted, warmer than Khorne Red.

Can I use Brown instead of Khorne Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Brown is noticeably lighter, more muted, warmer than Khorne Red.

Can I use Khorne Red instead of Brown?

The same difference applies the other way round: Khorne Red is noticeably darker, more saturated, cooler.

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.