Gravelord Grey vs Nighthaunt Gloom

How close are they?

ΔE 23.6, loose: different enough that you should pick on purpose. Nighthaunt Gloom is noticeably lighter, much more saturated than Gravelord Grey.

Can I use Nighthaunt Gloom instead of Gravelord Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Nighthaunt Gloom is noticeably lighter, much more saturated than Gravelord Grey.

Can I use Gravelord Grey instead of Nighthaunt Gloom?

The same difference applies the other way round: Gravelord Grey is noticeably darker, 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.