Purple People Eater vs Alien Purple

How close are they?

ΔE 19.1, loose: different enough that you should pick on purpose. Alien Purple is noticeably lighter, more saturated than Purple People Eater.

Can I use Alien Purple instead of Purple People Eater?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Alien Purple is noticeably lighter, more saturated than Purple People Eater.

Can I use Purple People Eater instead of Alien Purple?

The same difference applies the other way round: Purple People Eater is noticeably darker, 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.