Rainy Gray vs IDF Isr. Sand Grey (61-73)

How close are they?

ΔE 8.8, close: similar, with a visible difference side by side. IDF Isr. Sand Grey (61-73) is a little darker than Rainy Gray.

Can I use IDF Isr. Sand Grey (61-73) instead of Rainy Gray?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). IDF Isr. Sand Grey (61-73) is a little darker than Rainy Gray.

Can I use Rainy Gray instead of IDF Isr. Sand Grey (61-73)?

The same difference applies the other way round: Rainy Gray is a little 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.