Transparent Purple vs Ink Blue

How close are they?

ΔE 26.2, loose: different enough that you should pick on purpose. Ink Blue is much more muted, cooler than Transparent Purple.

Can I use Ink Blue instead of Transparent Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Ink Blue is much more muted, cooler than Transparent Purple.

Can I use Transparent Purple instead of Ink Blue?

The same difference applies the other way round: Transparent Purple is much 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.