Bony Matter vs Mummy White

How close are they?

ΔE 7.1, close: similar, with a visible difference side by side. Mummy White is more muted, cooler than Bony Matter.

Can I use Mummy White instead of Bony Matter?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Mummy White is more muted, cooler than Bony Matter.

Can I use Bony Matter instead of Mummy White?

The same difference applies the other way round: Bony Matter 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.