ΔE 15.2, loose: different enough that you should pick on purpose. Knight-Questor Flesh is noticeably darker, more saturated than Ruddy Umber.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Knight-Questor Flesh is noticeably darker, more saturated than Ruddy Umber.
The same difference applies the other way round: Ruddy Umber is noticeably lighter, 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.
See Ruddy Umber on the colour wheel See Knight-Questor Flesh on the colour wheel
All matches: Ruddy Umber equivalents · Knight-Questor Flesh equivalents