Medium Blue vs Light Turquoise

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. Light Turquoise is a little darker, warmer than Medium Blue.

Can I use Light Turquoise instead of Medium Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Light Turquoise is a little darker, warmer than Medium Blue.

Can I use Medium Blue instead of Light Turquoise?

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