Crusted Sore vs Red Oxide

How close are they?

ΔE 19.9, loose: different enough that you should pick on purpose. Red Oxide is a little lighter, more saturated, warmer than Crusted Sore.

Can I use Red Oxide instead of Crusted Sore?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Red Oxide is a little lighter, more saturated, warmer than Crusted Sore.

Can I use Crusted Sore instead of Red Oxide?

The same difference applies the other way round: Crusted Sore is a little darker, more muted, cooler.

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.