Macragge Blue vs Phthalo Blue GS

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Phthalo Blue GS is a little darker, more saturated, warmer than Macragge Blue.

Can I use Phthalo Blue GS instead of Macragge Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Phthalo Blue GS is a little darker, more saturated, warmer than Macragge Blue.

Can I use Macragge Blue instead of Phthalo Blue GS?

The same difference applies the other way round: Macragge Blue is a little lighter, more muted, 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.