Matt Orange vs Ink Yellow

How close are they?

ΔE 19.6, loose: different enough that you should pick on purpose. Ink Yellow is a little darker, much more saturated than Matt Orange.

Can I use Ink Yellow instead of Matt Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Ink Yellow is a little darker, much more saturated than Matt Orange.

Can I use Matt Orange instead of Ink Yellow?

The same difference applies the other way round: Matt Orange is a little lighter, much 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.