Bony Spikes vs Moon Mist Grey

How close are they?

ΔE 9.2, close: similar, with a visible difference side by side. Moon Mist Grey is a little darker, more muted than Bony Spikes.

Can I use Moon Mist Grey instead of Bony Spikes?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Moon Mist Grey is a little darker, more muted than Bony Spikes.

Can I use Bony Spikes instead of Moon Mist Grey?

The same difference applies the other way round: Bony Spikes is a little lighter, more saturated.

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.