Dark Rust vs Skavenblight Dinge

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Skavenblight Dinge is noticeably lighter, more muted, cooler than Dark Rust.

Can I use Skavenblight Dinge instead of Dark Rust?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Skavenblight Dinge is noticeably lighter, more muted, cooler than Dark Rust.

Can I use Dark Rust instead of Skavenblight Dinge?

The same difference applies the other way round: Dark Rust is noticeably darker, more saturated, warmer.

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.