Dead Flesh vs Mummy White

How close are they?

ΔE 21.3, loose: different enough that you should pick on purpose. Mummy White is noticeably lighter, more saturated, warmer than Dead Flesh.

Can I use Mummy White instead of Dead Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Mummy White is noticeably lighter, more saturated, warmer than Dead Flesh.

Can I use Dead Flesh instead of Mummy White?

The same difference applies the other way round: Dead Flesh 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.