ΔE 18.3, loose: different enough that you should pick on purpose. Spiritstone Red is noticeably darker, much more saturated than Matt Blood Red. They are different kinds of paint: AMMO by Mig Matt Blood Red is an ink, glaze or transparent paint and Citadel Spiritstone Red is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Spiritstone Red is noticeably darker, much more saturated than Matt Blood Red. They are different kinds of paint.
The same difference applies the other way round: Matt Blood Red is noticeably 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.
See Matt Blood Red on the colour wheel See Spiritstone Red on the colour wheel
All matches: Matt Blood Red equivalents · Spiritstone Red equivalents