ΔE 15.8, loose: different enough that you should pick on purpose. Deep Green is noticeably darker, more muted, cooler than Chromium Oxide Green Dark.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Deep Green is noticeably darker, more muted, cooler than Chromium Oxide Green Dark.
The same difference applies the other way round: Chromium Oxide Green Dark is noticeably lighter, 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.
See Chromium Oxide Green Dark on the colour wheel See Deep Green on the colour wheel
All matches: Chromium Oxide Green Dark equivalents · Deep Green equivalents