ΔE 12.2, fair: the same colour family, but not a straight swap. Light Gray is noticeably darker, cooler than Forest Faun.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Light Gray is noticeably darker, cooler than Forest Faun.
The same difference applies the other way round: Forest Faun is noticeably lighter, 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 Forest Faun on the colour wheel See Light Gray on the colour wheel
All matches: Forest Faun equivalents · Light Gray equivalents