Phoenix Flames vs Dark Yellow

How close are they?

ΔE 23.5, loose: different enough that you should pick on purpose. Dark Yellow is noticeably darker, much more muted, cooler than Phoenix Flames.

Can I use Dark Yellow instead of Phoenix Flames?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Dark Yellow is noticeably darker, much more muted, cooler than Phoenix Flames.

Can I use Phoenix Flames instead of Dark Yellow?

The same difference applies the other way round: Phoenix Flames 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.