Base Green (Protective) vs Steel Legion Drab

How close are they?

ΔE 16.0, loose: different enough that you should pick on purpose. Steel Legion Drab is noticeably lighter, warmer than Base Green (Protective).

Can I use Steel Legion Drab instead of Base Green (Protective)?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Steel Legion Drab is noticeably lighter, warmer than Base Green (Protective).

Can I use Base Green (Protective) instead of Steel Legion Drab?

The same difference applies the other way round: Base Green (Protective) is noticeably darker, cooler.

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.