Yellow FS33531 vs Light Yellow

How close are they?

ΔE 12.3, fair: the same colour family, but not a straight swap. Light Yellow is a little lighter, more saturated than Yellow FS33531.

Can I use Light Yellow instead of Yellow FS33531?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Light Yellow is a little lighter, more saturated than Yellow FS33531.

Can I use Yellow FS33531 instead of Light Yellow?

The same difference applies the other way round: Yellow FS33531 is a little darker, 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.