Sanguine Base vs Red

How close are they?

ΔE 26.5, loose: different enough that you should pick on purpose. Red is noticeably lighter, much more saturated, cooler than Sanguine Base.

Can I use Red instead of Sanguine Base?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Red is noticeably lighter, much more saturated, cooler than Sanguine Base.

Can I use Sanguine Base instead of Red?

The same difference applies the other way round: Sanguine Base is noticeably darker, much more muted, 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.