Mid Brown vs Flesh Wash

How close are they?

ΔE 23.6, loose: different enough that you should pick on purpose. Flesh Wash is noticeably lighter, more saturated than Mid Brown.

Can I use Flesh Wash instead of Mid Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Flesh Wash is noticeably lighter, more saturated than Mid Brown.

Can I use Mid Brown instead of Flesh Wash?

The same difference applies the other way round: Mid Brown is noticeably darker, more muted.

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.