Spiritstone Red vs Raw Sienna

How close are they?

ΔE 41.0, loose: different enough that you should pick on purpose. Raw Sienna is noticeably lighter, much more muted, warmer than Spiritstone Red.

Can I use Raw Sienna instead of Spiritstone Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 41). Raw Sienna is noticeably lighter, much more muted, warmer than Spiritstone Red.

Can I use Spiritstone Red instead of Raw Sienna?

The same difference applies the other way round: Spiritstone Red is noticeably darker, much more saturated, cooler.

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.