Inferno Orange vs Medium Flesh

How close are they?

ΔE 17.1, loose: different enough that you should pick on purpose. Medium Flesh is noticeably lighter, more muted than Inferno Orange.

Can I use Medium Flesh instead of Inferno Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Medium Flesh is noticeably lighter, more muted than Inferno Orange.

Can I use Inferno Orange instead of Medium Flesh?

The same difference applies the other way round: Inferno Orange is noticeably darker, 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.