Light Soviet Khaki vs Undead Flesh

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Undead Flesh is a little lighter, much more muted than Light Soviet Khaki.

Can I use Undead Flesh instead of Light Soviet Khaki?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Undead Flesh is a little lighter, much more muted than Light Soviet Khaki.

Can I use Light Soviet Khaki instead of Undead Flesh?

The same difference applies the other way round: Light Soviet Khaki is a little darker, much more saturated.

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.