Jungle Green vs Valkyrie Yellow

How close are they?

ΔE 29.8, loose: different enough that you should pick on purpose. Valkyrie Yellow is noticeably lighter, more muted, warmer than Jungle Green.

Can I use Valkyrie Yellow instead of Jungle Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Valkyrie Yellow is noticeably lighter, more muted, warmer than Jungle Green.

Can I use Jungle Green instead of Valkyrie Yellow?

The same difference applies the other way round: Jungle Green is noticeably darker, more saturated, 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.