Legendary Red vs Fire Red

How close are they?

ΔE 29.0, loose: different enough that you should pick on purpose. Fire Red is noticeably darker, much more muted, cooler than Legendary Red.

Can I use Fire Red instead of Legendary Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Fire Red is noticeably darker, much more muted, cooler than Legendary Red.

Can I use Legendary Red instead of Fire Red?

The same difference applies the other way round: Legendary Red is noticeably lighter, much 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.