Tyrant Skull vs Ivory Light

How close are they?

ΔE 19.9, loose: different enough that you should pick on purpose. Ivory Light is noticeably lighter, much more muted than Tyrant Skull.

Can I use Ivory Light instead of Tyrant Skull?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Ivory Light is noticeably lighter, much more muted than Tyrant Skull.

Can I use Tyrant Skull instead of Ivory Light?

The same difference applies the other way round: Tyrant Skull is noticeably darker, much 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.