Abaddon Black vs Flat Black

How close are they?

ΔE 7.8, close: similar, with a visible difference side by side. Flat Black is a little lighter than Abaddon Black.

Can I use Flat Black instead of Abaddon Black?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Flat Black is a little lighter than Abaddon Black.

Can I use Abaddon Black instead of Flat Black?

The same difference applies the other way round: Abaddon Black is a little darker.

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.