Blood Red vs Seraphim Flesh

How close are they?

ΔE 41.4, loose: different enough that you should pick on purpose. Seraphim Flesh is a little lighter, much more muted than Blood Red.

Can I use Seraphim Flesh instead of Blood Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 41). Seraphim Flesh is a little lighter, much more muted than Blood Red.

Can I use Blood Red instead of Seraphim Flesh?

The same difference applies the other way round: Blood Red is a little darker, much 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.