Flesh Tearers Red vs Crimson

How close are they?

ΔE 16.9, loose: different enough that you should pick on purpose. Crimson is a little darker, more muted than Flesh Tearers Red.

Can I use Crimson instead of Flesh Tearers Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Crimson is a little darker, more muted than Flesh Tearers Red.

Can I use Flesh Tearers Red instead of Crimson?

The same difference applies the other way round: Flesh Tearers Red is a little lighter, 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.