Crimson vs Devil Red

How close are they?

ΔE 29.5, loose: different enough that you should pick on purpose. Devil Red is a little lighter, cooler than Crimson.

Can I use Devil Red instead of Crimson?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Devil Red is a little lighter, cooler than Crimson.

Can I use Crimson instead of Devil Red?

The same difference applies the other way round: Crimson is a little darker, 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.