Ice Yellow vs Lilith Yellow

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Lilith Yellow is a little darker, more saturated than Ice Yellow.

Can I use Lilith Yellow instead of Ice Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Lilith Yellow is a little darker, more saturated than Ice Yellow.

Can I use Ice Yellow instead of Lilith Yellow?

The same difference applies the other way round: Ice Yellow is a little 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.