Flesh Wash vs Umber Wash

How close are they?

ΔE 20.3, loose: different enough that you should pick on purpose. Umber Wash is noticeably darker, much more muted than Flesh Wash.

Can I use Umber Wash instead of Flesh Wash?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Umber Wash is noticeably darker, much more muted than Flesh Wash.

Can I use Flesh Wash instead of Umber Wash?

The same difference applies the other way round: Flesh Wash is noticeably lighter, 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.