ΔE 36.6, loose: different enough that you should pick on purpose. Crimson is a little darker, cooler than Demon Red.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 37). Crimson is a little darker, cooler than Demon Red.
The same difference applies the other way round: Demon Red is a little lighter, 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.
See Demon Red on the colour wheel See Crimson on the colour wheel
All matches: Demon Red equivalents · Crimson equivalents