Blue FS 35190 vs Aquamarine

How close are they?

ΔE 17.4, loose: different enough that you should pick on purpose. Aquamarine is noticeably lighter, more saturated, warmer than Blue FS 35190.

Can I use Aquamarine instead of Blue FS 35190?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Aquamarine is noticeably lighter, more saturated, warmer than Blue FS 35190.

Can I use Blue FS 35190 instead of Aquamarine?

The same difference applies the other way round: Blue FS 35190 is noticeably darker, more muted, 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.