Pylar Glacier vs Bright Slate Grey

How close are they?

ΔE 7.9, close: similar, with a visible difference side by side. Bright Slate Grey is more muted than Pylar Glacier.

Can I use Bright Slate Grey instead of Pylar Glacier?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Bright Slate Grey is more muted than Pylar Glacier.

Can I use Pylar Glacier instead of Bright Slate Grey?

The same difference applies the other way round: Pylar Glacier 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.