Flag Red vs Vermilion

How close are they?

ΔE 10.0, close: similar, with a visible difference side by side. Vermilion is a little lighter, more muted than Flag Red.

Can I use Vermilion instead of Flag Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Vermilion is a little lighter, more muted than Flag Red.

Can I use Flag Red instead of Vermilion?

The same difference applies the other way round: Flag Red is a little darker, more saturated.

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.