Fire Lizard vs Intense Yellow

How close are they?

ΔE 17.6, loose: different enough that you should pick on purpose. Intense Yellow is noticeably lighter, more saturated, cooler than Fire Lizard.

Can I use Intense Yellow instead of Fire Lizard?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Intense Yellow is noticeably lighter, more saturated, cooler than Fire Lizard.

Can I use Fire Lizard instead of Intense Yellow?

The same difference applies the other way round: Fire Lizard is noticeably darker, 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.