Grey Castle vs IDF Gray 2 (-1981 Golan)

How close are they?

ΔE 13.3, fair: the same colour family, but not a straight swap. IDF Gray 2 (-1981 Golan) is noticeably darker than Grey Castle.

Can I use IDF Gray 2 (-1981 Golan) instead of Grey Castle?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). IDF Gray 2 (-1981 Golan) is noticeably darker than Grey Castle.

Can I use Grey Castle instead of IDF Gray 2 (-1981 Golan)?

The same difference applies the other way round: Grey Castle is noticeably lighter.

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.