Celestra Grey vs Phthalo Turquoise Light

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Phthalo Turquoise Light is a little darker, much more saturated than Celestra Grey.

Can I use Phthalo Turquoise Light instead of Celestra Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Phthalo Turquoise Light is a little darker, much more saturated than Celestra Grey.

Can I use Celestra Grey instead of Phthalo Turquoise Light?

The same difference applies the other way round: Celestra Grey 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.