Imrik Blue vs Alien Purple

How close are they?

ΔE 21.9, loose: different enough that you should pick on purpose. Alien Purple is a little lighter, more saturated, warmer than Imrik Blue.

Can I use Alien Purple instead of Imrik Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Alien Purple is a little lighter, more saturated, warmer than Imrik Blue.

Can I use Imrik Blue instead of Alien Purple?

The same difference applies the other way round: Imrik Blue is a little darker, more muted, 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.