Catachan Flesh vs Blood Tracker Brown

How close are they?

ΔE 20.9, loose: different enough that you should pick on purpose. Blood Tracker Brown is a little lighter, much more saturated than Catachan Flesh.

Can I use Blood Tracker Brown instead of Catachan Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Blood Tracker Brown is a little lighter, much more saturated than Catachan Flesh.

Can I use Catachan Flesh instead of Blood Tracker Brown?

The same difference applies the other way round: Catachan Flesh 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.