Afterglow vs Fall Green

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Fall Green is a little darker, much more saturated than Afterglow.

Can I use Fall Green instead of Afterglow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Fall Green is a little darker, much more saturated than Afterglow.

Can I use Afterglow instead of Fall Green?

The same difference applies the other way round: Afterglow is a little lighter, much 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.