Electric Blue vs Rust

How close are they?

ΔE 55.0, loose: different enough that you should pick on purpose. Rust is noticeably lighter, much more muted, warmer than Electric Blue.

Can I use Rust instead of Electric Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 55). Rust is noticeably lighter, much more muted, warmer than Electric Blue.

Can I use Electric Blue instead of Rust?

The same difference applies the other way round: Electric Blue is noticeably darker, much more saturated, cooler.

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.