ΔE 16.3, loose: different enough that you should pick on purpose. Grey Brown is more muted, cooler than Burnt Umber Light.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Grey Brown is more muted, cooler than Burnt Umber Light.
The same difference applies the other way round: Burnt Umber Light is more saturated, 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.
See Burnt Umber Light on the colour wheel See Grey Brown on the colour wheel
All matches: Burnt Umber Light equivalents · Grey Brown equivalents