Nickel Azo Yellow vs Ink Red

How close are they?

ΔE 74.9, loose: different enough that you should pick on purpose. Ink Red is noticeably darker, more muted, cooler than Nickel Azo Yellow.

Can I use Ink Red instead of Nickel Azo Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 75). Ink Red is noticeably darker, more muted, cooler than Nickel Azo Yellow.

Can I use Nickel Azo Yellow instead of Ink Red?

The same difference applies the other way round: Nickel Azo Yellow is noticeably lighter, 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.