Soft Tone vs Caspian Flesh Wash

How close are they?

ΔE 18.9, loose: different enough that you should pick on purpose. Caspian Flesh Wash is noticeably lighter, more muted, cooler than Soft Tone.

Can I use Caspian Flesh Wash instead of Soft Tone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Caspian Flesh Wash is noticeably lighter, more muted, cooler than Soft Tone.

Can I use Soft Tone instead of Caspian Flesh Wash?

The same difference applies the other way round: Soft Tone is noticeably darker, more saturated, warmer.

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.