Ivory Light vs Rus. AF Grey Prot. Coat

How close are they?

ΔE 23.5, loose: different enough that you should pick on purpose. Rus. AF Grey Prot. Coat is noticeably darker, more saturated than Ivory Light.

Can I use Rus. AF Grey Prot. Coat instead of Ivory Light?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Rus. AF Grey Prot. Coat is noticeably darker, more saturated than Ivory Light.

Can I use Ivory Light instead of Rus. AF Grey Prot. Coat?

The same difference applies the other way round: Ivory Light is noticeably 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.