Flat Yellow vs Deep Yellow

How close are they?

ΔE 13.7, fair: the same colour family, but not a straight swap. Deep Yellow is a little darker, more muted than Flat Yellow.

Can I use Deep Yellow instead of Flat Yellow?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Deep Yellow is a little darker, more muted than Flat Yellow.

Can I use Flat Yellow instead of Deep Yellow?

The same difference applies the other way round: Flat Yellow is a little lighter, 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.