Dorn Yellow vs Septic Green

How close are they?

ΔE 25.4, loose: different enough that you should pick on purpose. Septic Green is noticeably darker, much more muted, cooler than Dorn Yellow.

Can I use Septic Green instead of Dorn Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Septic Green is noticeably darker, much more muted, cooler than Dorn Yellow.

Can I use Dorn Yellow instead of Septic Green?

The same difference applies the other way round: Dorn Yellow is noticeably lighter, much more saturated, 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.