Catachan Flesh vs Boot Strap Brown

How close are they?

ΔE 9.1, close: similar, with a visible difference side by side. Boot Strap Brown is a little lighter, more muted than Catachan Flesh.

Can I use Boot Strap Brown instead of Catachan Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Boot Strap Brown is a little lighter, more muted than Catachan Flesh.

Can I use Catachan Flesh instead of Boot Strap Brown?

The same difference applies the other way round: Catachan Flesh is a little darker, more saturated.

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.