Gypsum White vs USAF Light Gray

How close are they?

ΔE 5.9, very close: most people won’t see a difference side by side. USAF Light Gray is a little darker, more saturated than Gypsum White.

Can I use USAF Light Gray instead of Gypsum White?

Yes, for most jobs. Very close match (ΔE 6). USAF Light Gray is a little darker, more saturated than Gypsum White.

Can I use Gypsum White instead of USAF Light Gray?

The same difference applies the other way round: Gypsum White 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.