RAF Middle Stone vs Balor Brown

How close are they?

ΔE 9.0, close: similar, with a visible difference side by side. Balor Brown is a little darker, more saturated than RAF Middle Stone.

Can I use Balor Brown instead of RAF Middle Stone?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Balor Brown is a little darker, more saturated than RAF Middle Stone.

Can I use RAF Middle Stone instead of Balor Brown?

The same difference applies the other way round: RAF Middle Stone is a little 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.