Rage Brown vs Phoenix Orange

How close are they?

ΔE 20.7, loose: different enough that you should pick on purpose. Phoenix Orange is a little lighter, much more saturated than Rage Brown.

Can I use Phoenix Orange instead of Rage Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Phoenix Orange is a little lighter, much more saturated than Rage Brown.

Can I use Rage Brown instead of Phoenix Orange?

The same difference applies the other way round: Rage Brown is a little darker, much more muted.

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.