Blood Chalice vs Pyrrole Red

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Pyrrole Red is a little darker, much more saturated, warmer than Blood Chalice.

Can I use Pyrrole Red instead of Blood Chalice?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Pyrrole Red is a little darker, much more saturated, warmer than Blood Chalice.

Can I use Blood Chalice instead of Pyrrole Red?

The same difference applies the other way round: Blood Chalice is a little lighter, much more muted, 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.