Celestra Grey vs Mythic Turquoise

How close are they?

ΔE 19.7, loose: different enough that you should pick on purpose. Mythic Turquoise is much more saturated, warmer than Celestra Grey.

Can I use Mythic Turquoise instead of Celestra Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Mythic Turquoise is much more saturated, warmer than Celestra Grey.

Can I use Celestra Grey instead of Mythic Turquoise?

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