Psychic Shock vs Green Oxide

How close are they?

ΔE 20.6, loose: different enough that you should pick on purpose. Green Oxide is noticeably darker, more muted than Psychic Shock.

Can I use Green Oxide instead of Psychic Shock?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Green Oxide is noticeably darker, more muted than Psychic Shock.

Can I use Psychic Shock instead of Green Oxide?

The same difference applies the other way round: Psychic Shock is noticeably lighter, more saturated.

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.