Gravelord Grey vs Viking Grey

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Viking Grey is noticeably darker, more saturated than Gravelord Grey.

Can I use Viking Grey instead of Gravelord Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Viking Grey is noticeably darker, more saturated than Gravelord Grey.

Can I use Gravelord Grey instead of Viking Grey?

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