Ruby Alchemy vs Crimson Magenta

How close are they?

ΔE 26.4, loose: different enough that you should pick on purpose. Crimson Magenta is a little darker, more muted, cooler than Ruby Alchemy.

Can I use Crimson Magenta instead of Ruby Alchemy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Crimson Magenta is a little darker, more muted, cooler than Ruby Alchemy.

Can I use Ruby Alchemy instead of Crimson Magenta?

The same difference applies the other way round: Ruby Alchemy is a little lighter, 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.