Inktense Ochre vs Ink Yellow

How close are they?

ΔE 34.6, loose: different enough that you should pick on purpose. Ink Yellow is noticeably lighter, much more saturated, cooler than Inktense Ochre.

Can I use Ink Yellow instead of Inktense Ochre?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 35). Ink Yellow is noticeably lighter, much more saturated, cooler than Inktense Ochre.

Can I use Inktense Ochre instead of Ink Yellow?

The same difference applies the other way round: Inktense Ochre is noticeably darker, much more muted, 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.