Celestra Grey vs Trollblood Base

How close are they?

ΔE 20.7, loose: different enough that you should pick on purpose. Trollblood Base is noticeably darker, much more saturated than Celestra Grey.

Can I use Trollblood Base instead of Celestra Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Trollblood Base is noticeably darker, much more saturated than Celestra Grey.

Can I use Celestra Grey instead of Trollblood Base?

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