Light Soviet Khaki vs Sandstorm

How close are they?

ΔE 19.3, loose: different enough that you should pick on purpose. Sandstorm is noticeably lighter, warmer than Light Soviet Khaki.

Can I use Sandstorm instead of Light Soviet Khaki?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Sandstorm is noticeably lighter, warmer than Light Soviet Khaki.

Can I use Light Soviet Khaki instead of Sandstorm?

The same difference applies the other way round: Light Soviet Khaki 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.