Vampire Red vs Mephiston Red

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Mephiston Red is a little darker, more saturated, warmer than Vampire Red.

Can I use Mephiston Red instead of Vampire Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Mephiston Red is a little darker, more saturated, warmer than Vampire Red.

Can I use Vampire Red instead of Mephiston Red?

The same difference applies the other way round: Vampire Red is a little lighter, more muted, 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.