Knight-Questor Flesh vs Sangria Red

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Sangria Red is a little darker, much more saturated than Knight-Questor Flesh.

Can I use Sangria Red instead of Knight-Questor Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Sangria Red is a little darker, much more saturated than Knight-Questor Flesh.

Can I use Knight-Questor Flesh instead of Sangria Red?

The same difference applies the other way round: Knight-Questor Flesh is a little lighter, much 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.