Yellow Bone vs Tyrant Skull

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Tyrant Skull is noticeably darker, more saturated than Yellow Bone.

Can I use Tyrant Skull instead of Yellow Bone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Tyrant Skull is noticeably darker, more saturated than Yellow Bone.

Can I use Yellow Bone instead of Tyrant Skull?

The same difference applies the other way round: Yellow Bone is noticeably lighter, more muted.

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.