Incubi Darkness vs Cobalt Turquois

How close are they?

ΔE 17.6, loose: different enough that you should pick on purpose. Cobalt Turquois is noticeably lighter, more saturated, warmer than Incubi Darkness.

Can I use Cobalt Turquois instead of Incubi Darkness?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Cobalt Turquois is noticeably lighter, more saturated, warmer than Incubi Darkness.

Can I use Incubi Darkness instead of Cobalt Turquois?

The same difference applies the other way round: Incubi Darkness is noticeably darker, 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.