ΔE 19.5, loose: different enough that you should pick on purpose. Aquamarine is a little lighter, cooler than Cobalt Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Aquamarine is a little lighter, cooler than Cobalt Green.
The same difference applies the other way round: Cobalt Green is a little 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.
See Cobalt Green on the colour wheel See Aquamarine on the colour wheel
All matches: Cobalt Green equivalents · Aquamarine equivalents