Light Phthalo Blue vs Verdigris

How close are they?

ΔE 15.4, loose: different enough that you should pick on purpose. Verdigris is a little lighter, much more muted, warmer than Light Phthalo Blue.

Can I use Verdigris instead of Light Phthalo Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Verdigris is a little lighter, much more muted, warmer than Light Phthalo Blue.

Can I use Light Phthalo Blue instead of Verdigris?

The same difference applies the other way round: Light Phthalo Blue is a little darker, much 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.