Grass Green vs Afterglow

How close are they?

ΔE 17.9, loose: different enough that you should pick on purpose. Afterglow is noticeably lighter, more muted, warmer than Grass Green.

Can I use Afterglow instead of Grass Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Afterglow is noticeably lighter, more muted, warmer than Grass Green.

Can I use Grass Green instead of Afterglow?

The same difference applies the other way round: Grass Green is noticeably darker, more saturated, cooler.

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.