Rakarth Flesh vs Moonstone Grey

How close are they?

ΔE 9.5, close: similar, with a visible difference side by side. Moonstone Grey is more muted than Rakarth Flesh.

Can I use Moonstone Grey instead of Rakarth Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Moonstone Grey is more muted than Rakarth Flesh.

Can I use Rakarth Flesh instead of Moonstone Grey?

The same difference applies the other way round: Rakarth Flesh is 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.