Red Copper vs Evil Forest

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Evil Forest is noticeably darker, more saturated, cooler than Red Copper.

Can I use Evil Forest instead of Red Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Evil Forest is noticeably darker, more saturated, cooler than Red Copper.

Can I use Red Copper instead of Evil Forest?

The same difference applies the other way round: Red Copper is noticeably lighter, more muted, 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.