Tyrant Skull vs Zombie Rot

How close are they?

ΔE 16.0, loose: different enough that you should pick on purpose. Zombie Rot is noticeably darker, more saturated, cooler than Tyrant Skull.

Can I use Zombie Rot instead of Tyrant Skull?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Zombie Rot is noticeably darker, more saturated, cooler than Tyrant Skull.

Can I use Tyrant Skull instead of Zombie Rot?

The same difference applies the other way round: Tyrant Skull is noticeably lighter, more muted, warmer.

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.