Trollslayer Orange vs Phoenix Red

How close are they?

ΔE 22.0, loose: different enough that you should pick on purpose. Phoenix Red is noticeably darker, more muted, cooler than Trollslayer Orange.

Can I use Phoenix Red instead of Trollslayer Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Phoenix Red is noticeably darker, more muted, cooler than Trollslayer Orange.

Can I use Trollslayer Orange instead of Phoenix Red?

The same difference applies the other way round: Trollslayer Orange is noticeably 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.