ΔE 15.1, loose: different enough that you should pick on purpose. Inktense Olive is a little darker, cooler than Agrax Earthshade. They are different kinds of paint: Citadel Agrax Earthshade is a wash/shade and Scale75 Inktense Olive is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Inktense Olive is a little darker, cooler than Agrax Earthshade. They are different kinds of paint.
The same difference applies the other way round: Agrax Earthshade is a little lighter, 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 Agrax Earthshade on the colour wheel See Inktense Olive on the colour wheel
All matches: Agrax Earthshade equivalents · Inktense Olive equivalents