ΔE 12.5, fair: the same colour family, but not a straight swap. Light Phthalo Green is a little lighter, more saturated than Pastel Seafoam. They are different kinds of paint: Army Painter Pastel Seafoam is a one-coat contrast-style paint and Golden Light Phthalo Green is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Light Phthalo Green is a little lighter, more saturated than Pastel Seafoam. They are different kinds of paint.
The same difference applies the other way round: Pastel Seafoam is a little darker, 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.
See Pastel Seafoam on the colour wheel See Light Phthalo Green on the colour wheel
All matches: Pastel Seafoam equivalents · Light Phthalo Green equivalents