Sybarite Green vs Cobalt Green

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Cobalt Green is noticeably lighter, cooler than Sybarite Green.

Can I use Cobalt Green instead of Sybarite Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Cobalt Green is noticeably lighter, cooler than Sybarite Green.

Can I use Sybarite Green instead of Cobalt Green?

The same difference applies the other way round: Sybarite Green is noticeably darker, 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.