Bluish Grey vs Regiment Grey

How close are they?

ΔE 8.0, close: similar, with a visible difference side by side. Regiment Grey is more muted than Bluish Grey.

Can I use Regiment Grey instead of Bluish Grey?

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

Can I use Bluish Grey instead of Regiment Grey?

The same difference applies the other way round: Bluish Grey 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.