Mead Violet vs Sombre Grey

How close are they?

ΔE 16.7, loose: different enough that you should pick on purpose. Sombre Grey is more muted, cooler than Mead Violet.

Can I use Sombre Grey instead of Mead Violet?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Sombre Grey is more muted, cooler than Mead Violet.

Can I use Mead Violet instead of Sombre Grey?

The same difference applies the other way round: Mead Violet is more saturated, warmer.

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.