Archangel Red vs Blood Red Skies

How close are they?

ΔE 16.6, loose: different enough that you should pick on purpose. Blood Red Skies is a little lighter, more muted, cooler than Archangel Red.

Can I use Blood Red Skies instead of Archangel Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Blood Red Skies is a little lighter, more muted, cooler than Archangel Red.

Can I use Archangel Red instead of Blood Red Skies?

The same difference applies the other way round: Archangel Red is a little darker, more saturated, warmer.

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.